Hi Da-anda,
I do appreciate the point you are making.
Just to be clear, i'm not talking about addons in the ultimate sense - just the WIP skins in the repo outlined here:
http://forum.xbmc.org/showthread.php?tid=159372.
To my knowledge, there is no equivalent repo for the other types of addons (I for one do not consider a skin well described as being an addon, but that's a conversation for another day!) I would not wish to set the addon-frontend awash with half-formed thoughts and buggy betas.
Clashes of addon ID's need not be a problem as a single skin cannot / should not be in both repo's at the same time. As both repo's are controlled by Team-XBMC, mandating certain ID practices for the benefit of the frontend shouldn't be too difficult. A simple flag in the final XML feeding the frontend could indicate their status (beta etc) - anyway you catch my drift..
I highlight this in the knowledge that developing and contributing a skin takes a considerable investment from your user community. In many cases it is years of work.
I do strongly feel that supporting the up and coming skinners is worthy of a bit of extra effort, and presenting the more advanced ones on the front-end is a solid motivator. Far too many skinners simply give up.