I understand limitation of current Arcade setup -16 colors for sprite/tile means only 4 bits per pixel. But maybe its possible to use more than one color palette for different game parts - tiles, background, sprites?
Tiles could have different palette for each 16 sets of 4x4 tile set.
Impact on memory would be minimal. Only problem could be rendering engine.
But advantages are worth trying
After looking at source code I can see that screen buffer is using half bytes per pixel, after this solution it would require additional 10k of memory.
On other hand everything could be easy implemented using this experimental editor
Just think about those endless possibilities of easy importing and sharing tilesets and characters