I’m not sure if it fits your use case but the Evercade VS is essentially this. Evercade carts are SD flash mapped to a Game Boy pin out (the first 8 pins are the same as an SD card). It’s both easy to read carts as well as get a flash cart for running arbitrary ARM code.
Blaze changed the way the Evercade EXP reads carts, however, and it seems like the console no longer reads carts, or at least doesn’t after the first time.
Blaze changed the way the Evercade EXP reads carts, however, and it seems like the console no longer reads carts, or at least doesn’t after the first time.