I would install a cheap used known-good multifunction switch.
we know the wipers are controlled through this part
we know the lights are wired through this part(hi/lo beams/passing beams)
that is the ONLY "correlation" those two "functions" share in a mechanical part
just my 5 cents
my 94 lost brake lights one day...
bulbs = good
BOO switch = good
CHMSL = worked....
but the outer brake lights did not.
turned out to be the MF switch....the brake lights are wired through that switch because of the HAZARDS.
Just give it a shot and see