From my limited knowledge of PowerShot firmware, the lens communication is initiated from the main ARM CPU, so - at least in theory - it should be doable. You will have to reverse engineer Canon's assembly code and patch it somehow, and this step might be non-trivial.
I'd stay away from DIGIC 6 for this kind of modification, though. At least on DSLR, we couldn't find a way to patch ROM routines in Canon firmware (at the time of writing). Patching ROM contents currently works on DIGIC 2, 3, 4, 5 (via cache hacks), and also on 7 and 8 (by reconfiguring the MMU). Unless somebody at CHDK figured it out for D6 meanwhile
