This question comes up regularly. There are more people considering moving from PA to CBA, and giving it a go. I know several of them personally and all but one eventually gave up, not counting my wife and myself. My wife and I started to learn the CBA (C system) after about 40 years on the PA. Initially we could not play anything but now, after 9 years of practice, we can play everything again and even prima vista is beginning to work better and better.
For french musette the PA versus CBA difference is not that great. For the most part it does not require huge hands on PA. The CBA is a must when going to music composed or arranged for it, making use of large distances (like playing notes together that are 2 octaves apart).
When we were in the transition period we had the most difficulty trying to learn something on CBA that we previously learned on PA. But that too disappears and in fact Im finding that already knowing how a song goes greatly helps with finding the notes quickly enough on the CBA.
I would suggest concentrating on just one system. We stopped playing PA altogether (with a small exception and also still playing the piano). Once you become good enough on CBA there simply is no turning back. But it takes time and perseverance to get there.
