Come out of the top of the tailgate, where the rubber boot (wiring harness cover) for the tailgate lights, wipers, etc. Then follow one of the roof rails forward to your light bar. This way you won't have to drill another hole, just modify the rear rubber wiring harness cover.
But you will have to get the wiring from your switch to the top rear.
I'm looking to do something very similar - but was looking at some Jeep Liberty types of enclosures. I like the bumper mounts, but I've already got a fishing rod rack on there, so these would be a better fit for me.
I have an '04 XT, I'll give it a try and see what I can come up with and I'll post all the picts.
I currently have Hella FF500 mounted in my grill that are attached to the upper radiator mount. I made some brackets that hold them out front of the grille just in front of the hood. They Rock !!! To bad they are to slim to convert to HID.