Nice, but.You should expand the resolution by default, more than one spritesheet.Easy using of own palettes.What happens when in use sprites with own palettes?!?No restriction of tiles.If i wanna use pico 8, i use pico 8. I like your system but it needs more possibilities.
Having more than one spritesheet is something I’m exploring. But you can use your own palette already which is nice: https://usagiengine.com/#custom-palettes-palettepng