When building a power harness, just bring a single line out to a suitable "aux power" socket/tail. From that socket/tail you can feed all your present/future peripheral power needs, via a custom "sub-harness", a custom "aux power distribution board" or whatever. For example, a tiny piece of Veroboard with some 3-way 0.1" headers lined up along it, then use standard servo plugs to feed power to whatever you need.
