I didn't say it was logical to do it, just that we could if we really wanted to
If you could find a classic gameboy - the huge white one, you could rip the guts out of it, cut a bigger hole for the screen, rip the guts of an old PPC [or a 1910 - since you're only going to be playing gameboy on it anyways

] and put it in the gameboy shell. Doesn't seem too complicated. Now, rewiring the old GameBoy pad and buttons to the PPC's.... I don't know, would it be possible?
Definite style points for whoever pulls it off.