OP, Game Boy is two words. I can't even read your whole post; it's offensive to my eyes.
In response to "but they don't make screens in that aspect ratio anymore," I point to the Neo-Geo X. They were like "who cares?" and put a widescreen in there anyway. You just have black borders or a stretched screen, your choice. Neither is ideal, of course, and I'm not sure whether that would represent a Nintendo-level of polish. But let's face it: a Game Boy redesign, at this point, would NOT feature the same kind of LCD we had all those years ago. There's zero chance of that. So they might as well manufacture a screen that won't drive up the cost per unit too much.
Honestly, I think the best solution would be to make a screen with the same ratio as the GBA and then to letterbox older GB games. And yeah, throw all those games in one unit. I mean, why not...?
Another idea: sell cartridges. One with original GB games, one with GBC games, one with GBA games...is that ridiculous?