I know that thanks to easiness Pico-8 is quite popular, and good for introducing programming to kids, but if I understand correctly biding script language to core GLB isn't enough, you would need to have small 2d engine/suite to simplify everything, to have commands like LoadBackground(image.png), ShowBackground(), LoadUnit(player_sprite.png), and so on available in simple way in some kind of shell called fantasy computer, that would have also built-in features like sprite/map editor and so on. This itself would be pretty large project additionally beside core GLB, maybe someone is already working on something like this or you may start such thing ;]