i actually like the power levels of the Summers. I wish mutants wouldnt have such a problem controlling their powers though. Rogue has lost control how many times? I know they usually get their powers during puberty (although it seems to be starting younger and younger) but Scott Summers is like 40. He should be able to control his powers without the visor.
If he returns, have him pop up in someone else's book. Make him the focus of a Green Arrow arc or something and use that as an excuse to bring in a Bat-Family character in order to deal with him. Use that as build up until he makes another solid return in a Batman book.
Joker in all about Batman. He wouldnt go after another hero unless it was to affect Batman. Joker would need to go after Batman ripoffs (Green Arrow could fall in to this category but would likely go after more obvious ripoffs), the Justice League (he could do a rehash of Justice League: Doom), or go after Selina Kyle.
After hoping for years that the Wally West we all knew and loved would be left alone some how and brought back into the fold even if it was in Red Hood and the Outlaws. I now consider Wally West dead. This new Wally West is a new character the (besides the suit) i dont like. I am still giving him a chance but unless some Multiversal event changes things we will never see the Wally West we all used to know