First, I'm fine with calling more story ideas related to technology to be on-topic. That said, the official rules are that questions should be related to world design. So if everyone or even a large minority had cars like this, it would be on-topic. But this is about a specific individual who wants to have a special car. If this isn't covered under the prohibition against questions about individual actions to enable a specific plot point, what is?
If this question is on-topic, we should change the rules to cover it.
For example, questions are welcome
as long as they are not about:
- Actions of individual characters, rather than elements of the world they
- Elements of plot
Those two rules seem to pretty clearly exclude this question to me. The plot is that Alice and Bob have this relationship. How can the individual Alice alter her car so that only she can drive it?
Want a similar question that would be more borderline? What physical property of the universe should I change such that Bob can't drive Alice's car? Example answers might be to make Bob and Alice radically different sizes. Or to give Alice a magic power that allows her to start cars. Those are changes to the world or universe, not to one specific vehicle that is different from everyone else's vehicle.
Again, I don't hate this question. I'm fine with rewriting the rules to cover this situation. But this question seems pretty clearly on the wrong side of the rules as currently written. Should it be? I don't know. But it is.