Custom anything will require special attention to detail. A platform such as a Subaru doesn't exactly have the most support for such things, but there is a surprising amount of aftermarket support for off-road mods.
As far as I know, usually trucks and police-platform vehicles (Crown Victoria, Charger, Impala, Taurus, Explorer, Tahoe, etc) will be more readily able to be outfitted with custom switches and other additional potential electrical loads.
What I've seen from some owners are the use of existing OEM switch locations to operate their additional accessories, otherwise, custom anything will leave it to you or whoever working on it to figure out an appropriate setup.
"Why would I want to profess my feelings for some 3D girl?" - Tomoya Aki from the anime Saekano