Here is a very simple idea, but depends on one question - do you really need to be able to raise them from the inside comfort of the cabin - or do you mind spending 90-120 seconds doing it manually?
If manual is okay, then it's cake. On the back side of the bumper, have 2 studs sticking outwards (towards the grill). Then have the lights mounted independently on a steel brackets w/ slots/holes in it, 2 at the bottom, 2 at top, same spacing as the studs. So just slip the bracket down over the studs and thread down a wingnut at whichever height yo uwant for the moment. Done... and will cost about $10 for all the parts...