I would go for a GH2/GH3 too. I've just picked a GH2 with kit lenses for 225 euro, so I have plenty of money for gear and even lenses. Can't figure out other way to better video camera + gear.
The crop factor is the key. You could go mft lenses, use an adapter which reduces de field of view or adapt lenses that are pretty wide. This is an article about the last option I give you: http://www.vintagelensesforvideo.com/kiev-16u-lenses/
Hope I could help!
My opinion: OF COURSE. Full creativity ever.
Right, I tried to say until 800. At 1600 it appears to be usable as you said, but right, flat + high iso in that camera = noise. I will hack my GH2 as soon as it arrives. Never have one in my hand, but guys, I watch videos where people use it in such a smart way they get the hell out of it. Don't know why, but the videos I prefer are shot with the Sanity patches, they get a lot of detail, sharpness and still good colors even if I rewatched Driftwood Moon t8, I still prefer that Sanity image.
I've just bought a GH2 mint with 14-42 lenses for 225 euros. Upgrade from Canon 600D, that GH2 has some organic look that I'm in love with :D