Sounds like you're running into a lot of the same issues I was having when I tried to tackle attaching heated mirrors to my USDM accord, lol.
I never considered a switch with a built in relay but I had both wiring diagrams. That was the easy part. The hardest was that I was gonna need to wire them up under the dash and tap into pre-existing relays and wiring setups. Ultimately it was just told much hassle. PFM are cool and all but if I really want them in, I'll fold them manually. Almost the same with heated mirrors. By the time I scrape the car or its heated enough for me to drive, the mirrors will be clear enough.