First... thanks to Wermy for the incredible instructions and custom parts. Thanks to Helder for the super-sweet all in one board. And thanks to AJRedfern for the awesome custom Gameboy Zero splash screen.
Here is what I did. It’s a ‘normal’ build with Helders AIO but without the SD card reader or power boost. My cost was $118 (including extra parts) due to parts I already had.
First things first… the elephant in the room...yes, I used a fully functioning original Gameboy for mine. “What?! How dare you!” Look, it has been in a box for 20+ years. I popped in Metroid II and tried playing for a week before deciding to gut the Gameboy. And it turns out there is a reason it’s been in a box for 20 years: it really sucks. It is impossible to play without perfect lighting and I would rather play an emulated back-lit LCD version. There was no GB nostalgia factor for me either and I would rather repurpose it then sell it. Vote me off the island if you must.

Power - I used a 1500mah Wii U battery and the charger from a portable cell phone charger I already had. I wanted to keep the battery compartment intact as much as possible and the battery fit almost perfectly. The charging board is mounted under the Gameboy metal plate so l can see the charge indicator lights through the cartridge slot. Battery life, unknown. But it lasts longer than my thumbs do playing on this thing. I have played for an hour and a half straight and had 2 of 4 charge lights still lit.
Screen cover – The plastic screen cover that comes on the back-up monitor was perfect. I simply peeled off the Gameboy plastic and used it as a template to cut the monitor plastic. All it needed was a little sharpie action on the round corner to finish the black border.
Issues... turns out my soldering is way better than my hot glue skills. Good grief, what a mess.
And the speaker is not very loud but the headphones are too loud. No idea what that's about yet.
I really want to get Kites AIO and do another one, but I need to finish my Wii U project first.