I think if the wipers can be left out of harms way and just use a switch I'd go for that. The splines are relatively soft and wont stand continuous on and off.
Teaching granny etc I know but I'd also drop a battery terminal off before fiddling around with the dash. I once had the choke cable touch a live on my TR6 when moving things behind the dash, it glowed red and cooked everything it touched.
