nesdev.org

I was thinking of 16k for code, and 512k with 16k banks, actually. But I could probably use another bank for code. And you know what, graphics won't be that big of a deal, because I won't have to redraw a single tile in another graphics data file. My game uses CHR RAM, of course, and each map has it's graphics info at the beggining, like a graphics header. It can take parts of different graphics files and store them in the pattern tables. I'll see how much space I have in the end, and I'll see which method I'll use for bit reversing...

If you're talking about FF7 (or anything on SUROM) you'd want to have at least 2 times separed 16kb ROM for main code, one fixed bank for the first chunk of 256kb, and one for the segond chunk.
Effectivly, if you're reversing a huge chunk of tiles, the table would be worth it, I haven't really think to that, but I think the other guy above is right.

You'd want to have a few routines common between both fixed banks, and swapping to either one for various department (graphics, field engine, battle engine, music, etc...)