Mobile rangers are great but they don't do everything. Personally, I would be anxious owning a Tesla as my primary car with SC 6 hours away. Teslas are a dream to drive, but if you end up needing a service center, SC 6 hours away can sour that dream very quickly. SC experience has been going down since M3's came out, but having it 6 hours away could make it a total nightmare. Of course, your car could end up being flawless too and service center availability never coming into play.
A as a side note, if I was buying a used Tesla from 3rd party, I would pay for an inspection by Tesla, maybe in a form of one of the major annual services (yea, it costs $700, but for me it would be worth to me as insurance - I'd do it only if I am ready to buy of course). I am not sure whether rangers can do a full annual service (things like alignment, drive unit fluid changes, etc), but maybe in areas without SC's they do more than where I live? Maybe call them and ask?