Stupid question: Why not make a Gameboy attachment for phones?

I'll preface this with letting you know I'm not a gamer. I just need to be told what wrong with this idea.

Nintendo takes 5-10 of its most beloved Gameboy games. I'm talking original Gameboy through GB color (i think) where it was just B A and a D-pad. Remake those games in something that'll run on iOS and/or Android. Most likely with updated sprites and graphics, but still 2D. Nintendo probably has the assets lying around, seeing as they frequently re-release older games (virtual console, etc). Games should have a switch or unlockable to play in original green and black or whatever too. For the nerds.

Develop an $50-$80 controller add-on that holds the phone in the same positioning of a gameboy, maybe even covering half the screen. B A Start Select and D-pad buttons give you the original experience.

Now you launch like this is a new console. 5-10 games hit the store at once, and the promise of continued development, and you try to drive people to pick up this piece of hardware. This would be the push you need to get a type of game controller standardized, such that then other developers can target it. Maybe you license the hooks for the controller or maybe youre just happy that youre selling more hardware.

This seems like it would be a good toe-in-the-water move to try out getting games on to other platforms, but still sort of controlling the experience and making hardware margins.

What have I got wrong? Is it not technically feasible? Even if they were to partner with apple and only target iOS to make compatibility easier. We have seen apple favor developers of games, giving them early hardware access so Apple can show it off at a keynote.