Probably a bit late now, but back in the day I did 3 Fiestas and a MK1 Focus... But back then wiring was easy - 1 wire per lamp & a common return!
I did the metalwork / dedicated wiring install for a Mk4 Mondeo, but had to pay an inordiate amount of money for a garage to plug in a laptop & poke it for 2 mins & tell the computer that it now had a tow module fitted!
But totally agree with the dedicated electrics - no reverse sensors going nuts when you go backwards, but more importantly the one you hope will never need in anger - the ABS / stability control knows you have a trailer on the back!