To be honest, I like the sound of all of those ideas really. #2 and #3 seem like they'd be the best to me, but any of them would work out pretty well.

...There is one thing I would like to ask, though, and I'll understand if the answer is no, but... In the event that we go with a crossover, do we have to stick to American comics for our characters? For some reason I kind of want to stick a Kamen Rider into a superhero crossover, see, but again I'll understand if you just want to stick to Marvel/DC/etc. ^^;