1: Write it anyway, but I'd suggest doing so under a name that you can't tie to any others, and if you do piss off a BNF, don't argue with them and go into hiding for a little while, maybe even take down the fic. It's very cool to challenge prevailing characterization, but doing so or even co-writing with or defending someone who does can eventually get you in trouble. It can even get you stalked or at the very least, make people a lot more willing to drag even a small later dispute with you to Fandom Wank.

My best advice would be, if at all possible, to write it, file the fic or the idea away somewhere, and hope the BNFs leave for another fandom. If they do, then your alternate characterization shouldn't be as much of an issue.

6: Word. Weepy ukes suck.

10: Word.