I made "enemy unit frames" out of nameplates a while back which might be easier to select with a controller, but there isn't any association with the physical location of the unit on-screen.
It'll be a lot easier to recreate with the new unit IDs, but given the nature of nameplates, you'll still probably have them constantly rearranging themselves as they spawn and die or move on and off the screen.
https://youtu.be/tIrSlYh-5ao
(It looks like you still can't embed a video in a post? I could have sworn there was a way to do this.)