You haven't been considering the potential memory problem. If you expand to 128 it might be okay, but 256 is definitely out of the question. These things require way too much memory, because I believe the sprites are all dumped into the memory - it would take significant rewriting of code to fix this.
Remember that EV was designed to work on pre-PPC machines as well.
It would always be nice to have more, but management might be harder - I don't see why a small increase can't be done though.
Mike Lee (Firebird)