I've hinted at it so much there's no point in keeping it under wraps any longer.
For the longest time, I've been working on a way to port GB games to the GBA.
What I ended up building is a modified GB to GBA emulator that targets a fantasy console instead - I call it the GB Bridge.
GB Bridge is basically a GBC with a different memory map, a bigger screen, and extra inputs.
The real trick is that I use special registers to trigger native GBA routines from the emulator - meaning that, while very hard to pull off, I can push things as much as I want.