Running multiple power to the roof racks....

[the evil twin]

They would be in a water tight metal enclosure. I've seen it done before and it looks fantastic would hardly know it was there unless you were looking for it

Agree...

I had mine in a black placcy enclosure with an O ring seal (Jaycar, DSE or similar) and used cable glands for the wiring entry.
It was behind one of the rack mount feet against a cross bar so looked factory if you even noticed it
Works great.

If you use relays then no need for wacking great 7 core trailer wire either.
I used data cable, flat or round doesn't matter.