As you no doubt expect, I'd find it utterly ridiculous.
But that sort of rhetorical question misses the point I was attempting to make. I'm suggesting that the general computing market has grown to the point that it is beginning to encroach on the car market, in much the same way that it encroached on the phone market before it. Just as the computing market commoditized the phone call by making it nothing more than an app among many others, so too is the computing market primed to commoditize cars by making them nothing more than yet another device that can run apps. The opposite, as per your question? Not so much, hence why I find the one utterly ridiculous and the other entirely plausible.
Moreover, the features that make cars distinct from both each other and the other products are increasingly less important and less relevant to consumers (as evidenced by the double-digit drop-off in car adoption and later age for first vehicles among the millennial crowd as compared to previous generations). As with you, I doubt that Apple will be able to come in with a car that outperforms everything else on the market, but what will that matter, if it does succeed in having good enough performance while adding value in the areas that modern consumers actually care about?
And, when you get down to it, modern electric cars are not particularly complicated machines. They're well understood, experienced people are readily available, Tesla demonstrated that a newcomer could out-engineer the incumbents after a single iteration, and so long as you have the deep pockets and the manufacturing/distribution capability to bring something to market, the biggest differentiator will be in terms of the design and polish, rather than the engineering. Plus, Apple gets to build on the backs of Tesla and others, since they have had the opportunity to watch its missteps and learn from them, they've reportedly been poaching its top engineers, and they've been gaining more experience over the last few years in working with the key materials that make up an electric car (e.g. aluminum, glass, LiON batteries, etc.).
Honestly, I'm inclined to view Tesla as the Palm/Handspring of the car world, with everything else out today being the car equivalent of the dumb phones from yesteryear. If Apple doesn't do it and Tesla doesn't do it, someone is going to be the one to come in and disrupt the car market, since it has been way too stagnant for way too long. I don't know that Apple will be the one to do it, but it's going to happen, and soon, and I firmly believe it will be a company from the Silicon Valley crowd that'll be the one to do it.