Answering first to last:
- If I had to choose I'd go with what I've heard: Myde, Lumaria, Relena, Rould (can't remember Luxord's suggested name..)
- I'm not sure how they would come to be. Just that they lost their hearts to darkness somehow.
- I would say yes. If all the original members were restored I'd assume these four would be as well.
- I'm hoping they return in KH3, but maybe they'll return in the next saga as their own group of mercenaries or whatever. Marluxia is menacing and clever so he could lead a major force.
I would like them to return as I said like a group of neutral mercenaries. Or I'd like Luxord to work solo, maybe even as a vigilante. Just don't give them keyblades! Please!