How hard would it be to do this?

[game-genie]

Yes, but seeing the descriptions and pics, they look just diffraction gratings projector.

I think the OP was referring to some sort of "scanner", not just spyro or stars, at least if i've understood right

Since he is willing to DIY something, it would be no problem to mod these ^^"
It would be also posible to dissasamble it and put it into a new case and add a spirograph etc.