In my opinion it would be more important to add support for Sony 3 1/2 floppy drive and external memory expansion.
A game using the extra 16KB RAM cartridge would have twice the space to store tiles (16KB VRAM + 16KB extra RAM). Long games could take a break between the stages and load the extra graphics from cassette or floppy disc ...

64 KB +64 KB games are not common, with is weird since the external RAM cartridges are in the MSX standard!!!