Honestly, i think this is hopeless without significant work. Also, the VPU is also woefully documented.
As it is, the games on both MelonDS & Desmume run at about 2~3 FPS.
I don't remember what was the bottleneck on MelonDS but when i profiled Desmume,
the interpreter was by far taking most of the CPU cycles, followed by the renderer.
I don't think we would need perfect accuracy for games (and we could always resort to specific game hacks) but even then, it would require like two JIT engines, preferably the ARM7 one running on the VPU and the ARM9 on the main cpu.
We already have an ARM7 recompiler available for MIPS32 but no such thing for the ARM9.
I hope Exophase releases his source code for Drastic because i think that's the only emulator that could potentially be made to run in an acceptable way. But If you want to tackle this task @StapleButter
then be my guest.