Razor!!!
I hear what your talking about, and something like that was similar to how we were looking at groups when the forum first got going, but it has a few problems:
1) a giant pain to implement
2) no idea how to do this without it leading to a bunch of insular communities that never interact at all. dotp has this problem already to a large extent, and it is also part of why it has been so hard to get rpg developed; people post where they are comfortable, and if you give people space to make their own little private areas, posts start drying up, and you end up with tasteslikespam.com
I get the logic behind it, and I like the idea of it, but the danger of 2) really makes me question how much 1) is really worth investing it, when it might actually hurt the forum in the long run. Sorta like letting women vote; it sounds good in theory, but look where it got us.
I see that, although I think 2) could be mitigated with some decent branding. call it a workshop instead of a group and make the main entrance be through your own user panel, and it'll feel much more like it's your space to work on projects, rather than a place to set up communities. you could even take out the ability to share it directly with others entirely, so that it would just be a private workspace, but that makes collaborations more difficult.
no solutions to 1) though. but I've seen talk in other threads (and I agree) that one of the best tools in building a community is immersion, so having as many of the tools people need on-site as possible is valuable. for instance, right now, I could get everything I want from this feature by going back to the mothership and doing my work there, but that's not spending time on NGA. so, while I don't imagine this is a near-term implementable feature, if this does wind up being a whole thing (and I've been gone for nine months, maybe that's no longer the goal) having a private section where I can segment and organize projects is a valuable tool to have.