I have individual 10k ohm resistors. I was wondering if there's a way to hack them temporarily on to the connections to see if that'll fix things before replacing RP6 outright. Possible?
Hmmm... would mean soldering to the pins of the chip. (2 pull up resistors, one for kclock, one for kdat).
If you had a IC socket to solder to, and plug the even CIA on top, then yes. I'd be wary about soldering direct to a CIA chip, they seem a bit fragile (very prone to static shock).
I've seen somebody blow up a CIA chip just doing a continuity test on a live Amiga (GadgetUK164). All he was doing was measuring voltage to the serial port.
If you have a socket, it's worth doing just to make sure it really does fix the keyboard problem.
Changing a resistor pack means dismounting the whole board, worth looking for any other faults first (battery? etc etc etc).