Not at all, it the same palette loop for 7 or 15 colors, so both are supported. Blitting would be faster in 7 colors mode. But you have to consider the NES can display up to 25 colors at once when combining all background and sprites colors. So I'd recommend to just use the 15 colors mode. It's going to be slower bu you do it once since it's a bitmap. And in such a mode and game you don't need 60fps (IHMO).His version does basically negate the benefit of using 3bit colors though? I would say whether 3 or 4 bits, whatever makes sprite blitting fastest is best; I really think that is going the be the bottleneck on this one. You should have loads of free ram on the 644 and SPI ram no matter what.
In my proposed mode, the right section is indeed plain mode 5(like mode 1 but with 8 bit vram index) to allow enough free cycles to intertwine the preload of the next row pixel from the spi ram. The whole bottom part with the MOVE, would be mode 3 with sprites to allow arbitrary movement. So it's a 3-in-one video mode. The bottom part would be allowed to take the whole screen to handle title screen etc.There would be some complication involved with sprites that overlap the SPI and tiles area, and though it could be done, Alec's idea seems more like mode 1 tiles that are 8x8 with no ram tiles for sprites over tiles. I thought that was no loss, but since then I see I overlooked the "MOVE" area at the lower left of the screen. You can free move the cursor over that part to select a direction. I have not played through the game, but you could probably also do that part as "snap to tile" like the rest of the menu is? It would definitely be easier for video mode code, at least for now it would be easier to get the video mode up and running to build motivation. My humble 2 cents.
Lee's line buffer idea sounds pretty good and would indeed speed up the blitting.