I got Nestopia to run an expanded ROM and it seemed to recognize it, but after looking at the technical docs I'm still not 100% sure it'll work. In the event that 33 can handle 256kb of PRG, splitting text between banks is very easy in most cases. I'd be willing to share some code or even assist with the hack. I don't think it would be too difficult.
Should be. Apparently Bakushou!! Jinsei Gekijou does use 256KB PRG.
(though Disch's doc claims 512KB is the limit (6-bit register = 64 banks = 64x8KB), though it doesn't seem it was used on commercial games)