Multi sprites:
color sprite:
I think it is very complex to implement all that
Oh, I also forgot the NUSIZn registers:
https://www.randomterrain.com/atari-2600-memories-batari-basic-commands.html#nus...
Though, since the tool is using the standard kernel, it won't be possible to reuse the sprite on multiple lines; still, it should be possible to use NUSIZn to change quantity and size for a single line.