From my couch thoughts and slight investigation, I believe similar can be done with the radar sensor for Model Y's. My 2023 MYLR has the radar connector in the frunk tub area behind the support beam. I noticed it while I was installing the homelink module. Physically I dont see why we aren't able to do the same with the front radar. Buy the bracket, screw, and radar module, install it behind fascia and add the radar heater element. Just artificial software limits are all thats blocking us.
I saw in some other threads on TMC that as long as you have a friendly, official Tesla Tech who can fully unlock the gateway then you can edit the specific configuration options, i.e. like leecox said telling the car what equipment it has installed. Besides reinstalling all the software after editing the configuration (which would be necessary since car needs to know which packages/software to include/exclude to run) there shouldnt be much other fuss.
Apparently there is a radar module in the interior as well, looks to be pointing inwards. Reminds me of those old ultrasonic alarm systems for cars sensing if someone got inside. But that interior radar shouldnt be needed to have a more smooth traffic aware cruise control operation which is what I'm aiming for. I don't like Tesla Vision TACC phantom braking on me; computer just not a good enough judge with looking thru a camera.
One can spend too much time surfing the service manuals.
Model Y Service Manual | Tesla
And yes I totally stand by the idea of being able to install those USS and enable them just like homelink except that creating the holes would be a large area for error, so I would still take that in to a SC to have it done.