It now works with the Rumble Pak!
I've just managed to implement a new feature... it is now compatible with the rumble pak! This means that if you use a N64 controller with a rumble pak inserted, it will rumble whenever a GameCube controller would otherwise be rumbling.
More testing is yet to be done... but this should work for any games which utilise the rumble feature of the GameCube controller. So for example, since the rumble feature was implemented for "Ocarina of Time and Master Quest" for the GameCube... it will now work with the rumble pak, just like it did on the Nintendo 64!
Bear in mind that no Wii Virtual Console releases actually have rumble implemented... so this will do nothing in Wii VC unfortunately. However, since other adapters implement this feature for non-VC games, I figured it was worthwhile to implement it in mine.