Teslas already have very strict (annoyingly strict) gating keeping specific functionality off of public roads (Summon). The drag mode thruster-assisted boost will probably leverage that. I also imagine that cameras on the car would stop it from being engaged if it detects humans in its firing area even when not on public roads.

The flying trim will never be sold to general consumers. Even the rear-thruster trim is currently listed at a $250,000 pre-order fee, which is a deposit for a fraction of the full cost of the car. Final cost will be over $1M. Any of the thruster variants will be extremely rare; like, the one guy in your city that has one will show it off at car shows twice a year, McLaren P1, level of rare.