Can't see any objection to that I assume its less than a 13 amp load,most are 500-1500 watts max.Try ro ensure the cable cannot chafe where it comes out of the wall and seal it ouside with mastic.If you drill the hole slightly uphill it will reduce the possibility of water ingress if you are on an exposed wall.
now thats a good idea about drilling up hill i like that!! my only other tip is to see how you get the bulb out before putting it up they can be a real b u g g e r once theyre up and in an awkward place.
Its a good idea to apply a bit of vaseline or similar to the cover screw when you install it. Moisture and heat will corrode the screw after time. Dont handle the lamp with bare fingers. Always install unit within 10% of the horizintal.