I guess now would be a bad time to tell you that the power window switches in my '88 535i were a neverending source of frustration... I just couldn't keep the damn things from oxidizing.
Fortunately once you've popped one apart and cleaned the contacts it's a 10 minute job next time around...
The nice thing about those switches is some of them are orange-red backlit which would look good in an Avanti interior. Might want to see if yours are like that. Don't have a pinout, sorry. The stock ones on an '88 were not backlit, but the ones that the BMW dealer sold as replacements about 1999ish were. (there was one that I couldn't bring back to life and had to replace; I put it on the sunroof so it wouldn't stick out like a sore thumb.)