1) Does this setup look feasable to you?
Looks OK. I would have to suggest the Hitec 555 RX instead of the GWS. Better range & les glitching!
2) Do you see any problems with it?
Everything else looks ok!
3) Have I forgotten anything?
Buy some more batteries!
4) What about the battery having a controller already? Does that mean I don't need an ESC? I thought ESC was used for servos too.
The battery doesn't have a Controller! The Motor your buying already has an ESC so you can remove this from your list:
ESC: GS-100E Speed Controller 5-Amp With Brake
Good Luck!