I've been wanting something like that for so long, haha.
Mostly due to the fact that when you report a layering problem, it doesn't get fixed for a really long time.
I think this would be a great change.
Another avatar related feature that I would die for. I see a million issues with a system like this, but if it was implemented as something you have to activate each time you want to use it, I think it would be awesome.
Perhaps it could be a "use at your own risk" type gaia labs feature for awhile? Especially since a feature like this would have uncountably many glitches and tweaks to make to it since we have items which lay on multiple layers at once.
SoliaOnline has this feature, or had, dunno haven't been on in a long time but as far as I knew there were no problems with their system.