I suppose that a true nudist utopia would be a world (or at least a society) in which everyone is a nudist. Perhaps this would work in microcosm - like within the context of an enclosed nudist resort, but maybe extended to the level of a whole, functioning city (why do we not already have one of these?). And that would be nice. But it's a little much to expect the whole world to get on board with the nudist philosophy, especially if, like me, you believe in the virtue of diversity (as a direct consequence of liberty; i.e., the freedom of choice). As such, I would be perfectly content to settle for a world that simply tolerates the practices of those who do choose to go nude (responsibly, in reasonable contexts).
Which is to say that this society would not consist of everybody being nude all of the time. Not even nudists at nudist resorts are nude all of the time. If you don't want to be nude in public, then by all means, wear clothes. And those who are nude would still have to follow the basic rules of etiquette that are already hard-coded into the nudist experience. Particularly, this would mean no sexual shenanigans, and carrying a towel when necessary, to use when sitting down - especially on public chairs and benches, and the like.
Also, nudity wouldn't necessarily be allowed just anywhere. Already in this society, we have a population that is capable of differentiating those contexts in which shirts and shoes are required, and those in which they are not. You have to be fully dressed when you go into a store or a restaurant, but nobody bats an eyelash at all the exposed skin at the local pool or beach. While it would be nice to have stores and restaurants that cater to a nudist demographic (and why not?), they don't all have to be, and I would be satisfied simply with a reasonable compromise - for example, clothing optional pools, but clothing-required grocery stores. (By the way, there's no reason there couldn't be sanitation requirements that dictate that all workers, even in nudist-friendly stores or, especially, restaurants, be clothed while on duty - this is not uncommonly the case at snack bars even at nudist resorts).
So, you see, it doesn't have to be a nudist free-for-all, just an elimination of the grand nudity taboo. It's no big deal if somebody takes the garbage out in their boxer shorts, so why do we make such a big fuss if somebody walks out to grab their morning paper in the buff? Doesn't it make perfect sense for somebody to gather up their dirty clothes, take them to the laundromat, and get them washed without wearing anything (except maybe a pair of flip flops, and a purse for their change)? A person shouldn't be required to wear a legally-mandated minimum of clothing for doing yard work on his own property, regardless of who might be able to see him from the street. And if somebody wants to go jogging at a local park on a hot, summer day, and doesn't like wearing sweaty clothes, they should be allowed to!
Implementation
Textiles have a lot of anxieties about what goes on within the boundaries of nudist resorts. But the existence of those resorts proves that nudists have it figured out. (And also that nudists aren't stupid - they'll wear clothes when it makes sense to, like when it's cold). Getting past all the logistical non-issues that we've brushed on above, a more legitimate concern about transitioning to a nudist-friendly society would be how the rest of the population (the non-nudists, that is) deal with the nudity.
As I've already mentioned, we would have to first get past the nudity taboo for this to ever work. Nudists prove that this is a fully surmountable obstacle - surround yourself with naked bodies, and you become desensitized to them. But that doesn't mean that this is an obstacle everybody wants to overcome. The majority of the population is probably perfectly comfortable not being desensitized to seeing ugly, naked bodies (not because naked bodies are inherently ugly, but because some of them are inevitably going to be). Is it fair to force them to acclimatize themselves? The answer to this question hinges on which you think is more important - the freedom of a person to choose how to dress, or the "right" of a person not to be exposed to certain sights, even in public.
Uncomfortable though it may be for some, I think any honest reading of the consequences of liberty would favor the former over the latter. As much as some people may be disgusted by public exposure to, for example, things like homosexuality, country music, or urban fashion, that's just a consequence of letting individuals choose how to live their own lives. The public space is a shared space for everyone to use, not a space where the dominant majority gets to dictate how everyone else will behave, forcing minorities to keep their "abnormalities" hidden behind tall fences, shuttered windows, and closed doors.
If enough of the population wants to be free from the sight of public nudity, they're welcome to try to band together and create isolated textile-only communities (and if you think that's backwards, do you think homophobia should be the default just because gay people are a minority, or do you believe that citizens of a free country have a responsibility to tolerate the proportion of their population that is gay?), but laws and restrictions against a person's freedom to choose how to dress (or not dress) in public spaces should not be tolerated in this free country.
Pitfalls
That having been decided, the remaining problem is the behavior of non-nudists confronted with the public exposure of people's bodies. One of the advantages of isolated nudist resorts is that they can control who gets to be there, which means they can weed out the people who can't behave or don't fit in, and all that's left are the friendly nudists. Like spreading Shaolin Kung Fu to the masses, the blanket freedom to be nude in public would be like opening the gates and letting just anyone stroll through.
Certainly, isolated communities could continue to exist even in the wake of decriminalized public nudity - so that those nudists who prefer not to be "gawked at", and don't want to have their pictures taken while nude, can limit their nude recreation to these semi-private places, like they do already. Meanwhile, the rest of us can enjoy some additional freedom to live our lives the way we want to. Plus, the erosion of the nudity taboo would drastically minimize (if not completely eliminate) the problem of naked pictures of you getting out, and would hopefully temper people's reactions to seeing naked bodies (if they're all over the place), similarly to the way it already happens to nudists in nudist resorts right now.
What's left? The people who aren't willing to play nice, and aren't satisfied with just snapping a picture from afar. We have enough problems in society today with people criticizing rape victims for wearing too little - what happens when creeps start harrassing nudists? I don't take that to be an argument against public nudity (just as I don't take it to be an argument against wearing miniskirts), but it is something to consider. We can hope, in an idealistic sort of way, that exposing the population to nudity would temper their behavior like it does with nudists, but the reality is probably that there will still be wild cards out there. And if anything, that's the one thing that might legitimately keep public nudity off the books.
A related issue would be people taking advantage of the freedom to be nude in order to more readily engage in sexual activities. As I've said, nudist resorts can exercise some control over what goes on inside their fences, but we obviously can't force the entire population to constantly be on their best behaviors. It would still be on the police to enforce rules against things like public indecency (re-written to include "simple nudity" as an explicitly allowed exception), but we all know that the existence of rules (and the threat of punishment) doesn't preclude people from breaking them.
Obviously (judging from my stance on this issue), I don't think it would necessarily be a bad thing if people were more open about sex in public, but that's a different hypothetical than the one we're talking about here. Still, even if public sex acts remain illegal - which would go a long way in discouraging them, if not quite eliminating them - I honestly don't think that seeing a rogue stiffy here or there is going to traumatize anyone, especially in a society where nudity itself is no longer taboo.
Liberty & Justice
To pursue a relevant tangent, I once read about a case where it was reported that masturbation was prohibited in prison, and I felt that that was kind of inhumane. But the rationale for that rule was as follows: if any prisoner used masturbation to intimidate or offend one of the [female] guards, it would be a simple, cut-and-dry matter to punish the prisoner, by only needing to prove that they were masturbating, rather than the subtler claim that the masturbation was being used to intimidate or offend. It shifts the burden of proof in order to favor the victim; but I'm wary of this practice, especially when it involves potential civil rights violations like restricting a person's freedom to masturbate (the restriction of which, barring in specific temporary contexts - like during a polite dinner party - should never be tolerated in a humane society, even among prisoners).
In reality, the rule is (allegedly) not widely enforced in contexts other than the one it was written for, but the fact remains that the law is written in an overly broad fashion, which opens the door wide open to abuses of authority. Just because the restriction against mere masturbation is not usually enforced, doesn't change the fact that masturbation is technically not allowed, and that whenever anyone does it, they are in breach of the rules, and subject to the whim of a guard who may (possibly unfairly) interpret it in such a way as to choose to enforce the infraction. I don't believe that's the way rules should be used.
When everybody is a criminal for engaging in normal, everyday behaviors, then those who are in authority are free to use their personal judgment in determining who among the entire population gets to be punished - and that judgment can be influenced by prejudices, or prejudiced superiors, or simple selfishness or cruelty. I feel sorry for victims of intimidation and such, but their plight does not justify a violation of the very principle of civil liberty and the right to a fair trial. (The issue of whether convicted prisoners deserve to have human rights is a separate one; I believe they do, but as this situation can be extrapolated to non-prisoner-related cases, I feel it is a moot point).
Anyway, I see the same kind of thing being tied in with the nudity taboo. Yeah, a lot of people are uncomfortable with nudity alone, but I feel like a lot of it is simply to shift the burden of proof. If somebody is committing public acts of lewdness, it is a lot easier to prove that they had exposed themselves than that they were doing anything specific while exposed, or for any specific (subjectively interpreted) motivation. Opening the door for the allowance of public nudity means that a person can whip their cock out at any given time (provided they're in a clothing optional zone), and for any given reason, and it would be tough to prove that they were doing anything wrong.
Still, as above, I don't think this is a justification for writing overly broad rules that restrict people's basic liberties (in this case, the liberty to be nude in public). And, as I've said, nudist resorts do a pretty good job of weeding out the creeps, so why can't law enforcement simply learn from them to tell the difference between somebody who is exercising their freedom to be nude versus somebody who is making a nuisance of themselves in a sexual manner? I think the world would be a better - not worse - place if that were to happen, and if we all, meanwhile, became more tolerant of seeing people's unclothed bodies.
