Cherokee 6 (PA32-300) has the 5 position selector, one for each tank and off. The Lance (PA32R-300) has two interconnected tanks on each side with a 3 position selector, left/right/off.
Whilst having a selector for each tank might complicate it slightly, the selector is in pretty good position under the throttle, so is not hidden from view or fiddly. I could see issues if a Lance pilot went back and flew one with minimal time on the books, there could be some assumptions made wrt fuel that might haunt them.
As far as standardisation goes, this is a 1977 machine. You will need some time travel kit to fight that war.