I think this could be one of the greatest things ever. It could also go terribly afoul. For some reason, I have greater confidence for the former than any "classic" Muppet project. I think there's a certain respect for the Fraggles, and they wouldn't suffer the dumbing down and cheapening that belies the core group.
Some important things, though, all five must take part, even if Jerry just dubs the Gobo voice. If he doesn't do that, it's pointless. Also, Jerry Juhl and all other creatives involved in the show's formation need to be a primary concern. He helped create these characters, and cannot be cast aside.
Another important note, I think, is that characters of Jim's and Richard's should be worked around and not recast. Not a big problem, as they were mainly secondary or only recurring. Gorgs and Heap and friends can be fit in, but no Junior. Gorg College sounded like a cute idea fitting of the sensibilities. Let's mainly focus on the core five, and also get some nice Sprocket in there. I am sorta surprised I've seen no mention of Doozers, either.
Anyways, Muppet characters curiously exploring the human world is the stuff that good Muppet movies are made of. Not retellings of old stories, not cheap, crude jokes. This could easily become an old-school feeling, super-enjoyable, and very meaningful movie. Jim concieved it to head towards world peace, and a full-length theatrical film could tell a marvelous story with a great message, and be really poinient in these crazy, paranoid times. Let's just not throw in a token Baretta-voiced new sidekick character to make lowbrow jokes and pop-culture references.
-Squigiman