Count me among those who doesn't understand how you can both trade for and extend George without gutting your team. I would suspect that the C's, if they are interested in trading for George, will trade for him (maybe with Bradley and Crowder?) and then try to sign him with bird rights at the end of next year.
Another thing to keep in mind: It was widely reported last year that George wasn't thrilled with playing power forward. If you've got both Hayward and George, there's no getting around that scenario. I think that's a lineup that could work in terms of winning basketball games (even as we'd get killed on the boards), but I don't think it would be appealing to George.
Maybe you could expand the deal a little bit with Bradley, Crowder, Rozier (picks) for George and Serahin (works in the NBA trade machine). Another cheap big they have is Lavoy Allen. Would help with big man depth. You are right though. I don't believe George has been too crazy about playing PF in the past.
Horford
Seraphin or room exception free agent (Zach Randolph for example)
George
Hayward
Thomas
You could still play George at PF in small ball lineups just not full time.