I don't mind the "giant" external one. It's easily mounted with the two holes and easily hidden outside the cabin. Can't even see it until you get down low and look for it when mounted where I have it. I expect I could even zip tie it to the grill and it would still work. When my custom plates arrive, I may do just that. Seems the receivers sense these things (almost) no matter where you put them.
I switched to the green plan for my daughter's Prius about 2 weeks after I received the external version for the Tesla. I was expecting another external transponder, but instead they sent a mini one to her - a (literally) green one. No idea what their logic is.