@fallen one
In-browser would be pretty cool, link it in your sig when you've got your WIP up!
As for the group idea:
IIRC, the TDK forum lacked a lot of focus. It was more just like TGC++. Of course, we would have to understand that naturally it wouldn't get updated as frequently as some boards since it's a smaller group of people, but I don't think it would be too unrealistic to expect some number of posts/messages per week/month to show some sort of progress or participation.
Remember that this is not about separating the men from the boys, but rather collaborative encouragement and discipline with more focus and filter than you'd get on a larger forum like TGC, TIGSource, Gamedev, IndieGamer, etc.
I think we would reasonably need and expect the following:

Frequency of post requirements, that could scale leniently of course (say you don't post for a while because you're making a big update)

Contributing quantifiable content to other users' projects - whether it's media, part of a design doc, an algorithm, or whatever

Schedule regular Skype/Wave/whatever communication service "Jams"--in order to simulate the notion of working with a team, you would sporadically post progress of your game.
Example:
Cash: Just got a call from my new consultant guy, also finishing up some terrain for level X
Fallout: How'd that go? Is he worth $100? Debugging my menu
Cash: It definitely is, check it out
Seppuku: /me is compiling the final build!
This isn't quite the same as bedroom coding with your friends, but it may establish a similarly encouraging and helpful work environment.

Because there will be regular updates, there must also be regular feedback with similar frequency requirements

Private pages which contain the discussions and collaboration amongst members, but also a public space showcasing the work of the collective's members
I know these bullets mention requirements, but in reality it's not like we'll spend the time writing our own custom forum expansions to accomodate this. This kind of community will need to require participation in order to not dissolve quickly, but the purpose of the group will always be to serve its members rather than follow some arbitrary membership requirements.