1. Who would you choose?:
The Joker
2. What would be the circumstances that would turn this Super Villain into a Superhero?:
After killing Batman, The Joker starts to lose interest in the life of the supervillain, so he crafts a new, heroic persona to fill the void left by Batman and move on to newer and bigger things. I mean, after all, he's been playing villainous roles for almost 15 years. An performer has to branch out, and that's how The Joker sees his life: a performance. He becomes a light hearted, wise cracking hero who gives any cheesy, silver age do-gooder a run for their money and is chock full of corny one liners, heartfelt speeches, and lots and lots of quips.
3. Would the other Superheroes accept the reformed Super Villain?:
At first, most would either find him annoying or think him a very brave, kind man who's good to have around. Of course, once they figure out who he really is, they freak the ****ing out because he's the ****ing Joker he's crazy as **** holy ****ing ****. Then they'd probably try to send him back to Arkham, because, let's face it: He's The Joker. He's crazy as ****. Holy ****ing ****. Only reason he's suddenly turned good is because of how ****ing crazy he is.
4. Would the general public accept the reformed Super Villain?:
At first, he's be a welcome relief in Gotham City. A public figure doing good in a way that's a bit more accessable than The Batman, even if The Batman got more actual crime fighting done. He'd do a lot more charity work and organizing of neighborhood watches than actual skull bashing, although there'd be a bit of that too, and his cheesy, old school personality would endear him to a lot of people. He'd become Gotham's Joshua Norton: Kind of eccentric guy who's pretty smart and does good things people like and listen to. But if his true identity were revealed to the public, which it probably would be...holy ****ing **** he's the ****ing Joker he's crazy as ****.
5. Would he or she get a secret identity?
As I already mentioned, yes. He'd have a cheesy, old school 50s super hero/adventurer persona.