I wouldn't buy a GBA classic with the exact dimensions of an old GBA, but as my second favorite handheld ever, I would absolutely LOVE some sort of classic loaded with games. Probably more than any alternative.
Here's a rough list, in no particular order, if I had to choose 20 (I tried to exclude ports of games you can play elsewhere for the most part):
- Castlevania: Aria of Sorrow
- Warioware, Inc.
- Advance Wars
- LoZ: The Minish Cap
- Metroid Fusion
- Fire Emblem
- Pokemon Ruby
- Tactics Ogre
- Mega Man Zero
- Breath of Fire II
- Kirby: Nightmare in Dreamland
- Final Fantasy Tactics Advance
- Golden Sun
- Sonic Advance
- Harvest Moon: More Friends of Mineral Town
- Metal Slug Advance
- Mario & Luigi: Superstar Saga
- Super Puzzle Fighter II
- The Lord of the Rings: The Return of the King
- Boktai: The Sun Is in Your Hand
Ideally, there'd be 25 games and I'd fill the last five slots with the classics:
- LoZ: A Link to the Past
- Super Mario World: Super Mario Advance 2
- Yoshi's Island: Super Mario Advance 3
- Final Fantasy VI Advance
- Pokemon FireRed
Then leave a little onboard storage and allow us to download more game packs in the future as they're licensed.
As for the hardware, I think they'd need to mimic the exterior form factor for most part but take liberties with the face of the device.
So, size up the screen so that it dominates the screen real estate more than the old one (shrinking the old black border) or, if you're feeling
wild, make the black border a software frame on the larger screen so you have image resizing options and the system UI has way more room to breathe. You'll have to move the dpad and face buttons further to the left and right, but improve their build quality (no squishy stuff) and it should be fine. Small speakers on both sides instead of one and a home button to the bottom right of the screen, opposite start and select.
You could slap in an old cheap 720p smartphone display and achieve 4.5x the pixel density when replicating the 240x160 resolution of the original games. The 1080x720p display would allow for different filters and effects to be overlaid on the image (screen door, simulated light bleed for the SP fans, etc.) and enables a clean and modern system UI.
Make it "Clear" but replicate the original GBA hardware beneath it with a print. In reality, it's a small processor and a rechargeable battery.
It would never happen like that, but god, I would slip that thing in my back pocket all the fucking time. More than my Switch, probably!