I don't see why it would be that hard.
Then do it.
CHDK can just execute the raw binary code in the file.
No you can't. What address is it loaded at ? How does it link to the OS and CHDK functions ? How do you compile and link your "raw binary" in the first place ? How do you ensure the instruction cache is updated to it actually gets executed when you jump to the start ?
Most loadable binary formats are aimed at machines with MMUs. CHDK cameras have a flat address space, which actually makes this quite a bit more difficult, and means you can't rely on standard tools. CHDK itself (like the factory firmware) is loaded at a fixed address, but this isn't a viable option for loadable binaries.
Granted, I don't know how to program that, but I would think the CHDK developers would.
Knowing how to do it, and having the time to do it are very different things.
