Bank/page switching is not too hard. You just need 3 extra digital pins. The Rugged Circuits QuadRAM is such an example. In the old days, 512KB VRAM is pretty awful lot considering lots of old monitors could only go up to 640480, some to 800600, but few capable of 1024*768. If you are smart enough, you keep what's changing most often on one bank and you don't have to switch very often. Just don't put text across bank boundaries.