I really only need Spotify and Navigation when driving.
And yes, I want to continue getting OTA software upgrades (ideally when not on my hotspot)
My understanding is that basic navigation works even without a subscription. Certainly this was true about two years ago. (I had one year of free premium connectivity when I bought my Tesla, but I let that lapse when covid hit, then picked it up again about a year ago.) There's no display of traffic data without premium connectivity, but the navigation is supposed to use that data when plotting a route. Also, there's no way to get satellite views without premium connectivity. AFAIK, using WiFi through a cell phone won't get these features back, but I could be mistaken about that. Thus, AFAIK a cell phone WiFi link will get you nothing extra compared to stock connectivity levels in terms of navigation. If I'm mistaken about any of this, somebody please correct me.
As to Spotify, you might consider using Spotify on your cell phone and then link that to the car via Bluetooth. This should work fine, but you'll need to use your phone to control and monitor the playback. Some features should still work via the car's controls (volume, pause playback, skip forward and back), but if you wanted to do something more complex, you'd need to use the phone's user interface, which might be more awkward -- and of course "more awkward" when driving can also mean "more dangerous." I don't use Spotify myself, so I'm unfamiliar with its user interface and capabilities, much less how
you use it, so I can't say whether this would be an important difference to you. FWIW, though, I use a podcast player on my phone to listen to podcasts while driving, and I have no problem with that approach. All of this works over Bluetooth with no WiFi hot spot required.