I like how it is, definitely a Unicorn. I've personally only seen backup sensors on some Limited and SR5. Not sure if that is a Gulf States Toyota port or dealer option. My donor OG TE rear bumper didn't have the backup sensor hole cut outs but the body shop I used was able to integrate it in with my center rear lower bumper cover.
If I would of known months ago about that Toyota part I definitely would of gone your route, it's more water crossing safe.
And you are correct the fender flares line bends on the OG TE bumpers will never match perfectly with other trim models but I wouldn't stress over it.