I can't see Apple (or any other car startup, for that matter) going any where near the dealership model. There are too many problems with it and too little flexibility. If it weren't for legacy agreements that effectively hamstring manufacturers, it's likely that there would have been some significant changes made years ago. Anyhow, Tesla has already done the hard work of confronting it and making consumers aware of an alternative.

The biggest problem will be dealing with their influence over state legislatures. Tesla already upset dealerships; the idea of someone like Apple (with their capital on hand, experience, and influence at the federal level) following in Tesla's footsteps will be enough to terrify dealerships into some pretty heavy-handed action.

As for the supply chains, there are a lot of differences between the supply chain for consumer electronics manufacturing and automobile parts, but Apple's experience is still intensely relevant. I think it's likely that they'll have a lot of successes in dealing with it, despite those differences.

The supply chain is on the other end of the process from the dealerships.

Supply chain -> Assembly (manufacturing) -> sales (Dealership)

Seems like for a distribution model, Apple would go the way of Tesla and forgo them entirely. In fact, it would be amusing to see Apple fight legal battles that help sell Teslas in states where they've outlawed it due to the huge dealer lobby. If anyone could slug that one out and win, Apple certainly has the expertise and capital to do it.

Tesla will have already won most the battles before Apple starts fighting, I'm guessing.

Indeed. I would be a little nervous if I were a traditional brick-and-mortar car dealer franchisee right about now. Because if Tesla gets the laws changed, what's to stop the big manufacturers from just selling direct as well.

Existing auto manufacturers have signed contracts with their existing dealers. All states have laws that protect those contracts. Tesla is not attacking those contracts and those laws.

Tesla's attacking laws that say that all new autos have to be sold by dealers. That's quite different, and only a few states have such laws.