One of the nice features of the coming mesh design is you can make your own custom template for clothing
It's a double edged sword. The downside being that without a clear standard, the market is going to fragment badly. Every creator will define their own UV mapping, and clothes from one creator will not match any other creator. You will then be tied to using only clothes from that given creator with your mesh avatar. I've seen this all too well from my years at Renderosity, and various creators making their own mesh figures (Victoria, Aiko, LaRoo,Stephanie, Poser std models, etc. ) LL's mesh may not be the best, but at least it sets a hard standard for clothing interoperability between creators.
I fear that standard will be lost in the coming months/years. (at least until creators learn how bad for business it ultimately is)
I'm not sure-- like you said, it won't be good for business to design a mesh that can only use one creator's clothing. Who would pay any significant amount of money for an avatar that could only wear clothing made by one person? Anybody doing their own UV mapping will probably go as close to "standard" as possible, and there are already mesh templates available for download, which again creates a standard.
Moreover, I'm doubting that creating entirely new meshes for human avatars will be particularly popular. Mesh feet, certainly, and probably heads, but entire replacement avatars? Even hands will be minimal, since extra bones for fingers can't be added. Mesh avatar replacements will be great for non-human avatars, making ferrets and cats and dragons, anything currently being replaced by prims, but besides all of the possibie compatibility problems, what would be the *point* of entirely new human avatars? And could any possible points outweigh the negatives?
So far as human avatars, the use for meshes is clothing and accessories. Jackets that move with your avatar, boots that flex at the ankles and knees, miniskirts that don't clip as soon as you move. And it'll be great to define individual UV maps for those things, but you don't need to re-map the avatar to UV map a jacket or a shoe. Those things might even replace parts of the avatar mesh, but there would be no reason to replace the entire thing. I can only think of two reasons to buy an avatar that isn't compatabile with the majority of clothing: if it's not human or if it's really, really cheap. Non-human and super-cheap are already seperate markets from the "regular" SL econemy.