I agree with the OP that Tesla should extend the warranty on the entire vehicle. This notion that the car will somehow require less maintenance than all other cars is completely unproven. Most of the fleet is still under warranty and there a lot of parts where the expected life, as Tesla sees it, is unknown. True, it would cost Tesla money, but they also have a lot to gain by making the brand standout -- even more than it already does.
I have the extended warranty, but there hasn't been much discussion about how it will actually play out since most owners haven't hit 50,000 miles yet. In addition, I expect that Tesla will actually provide a fair amount of goodwill fixes when the warranty expires, which may be a great outcome. Unfortunately, hit or miss application of goodwill fixes will undoubtedly create significant dissatisfaction for those folks that are not extended the goodwill for whatever reason.
Regardless, it's tough be in Tesla's shoes because everything it does, in every market, is so closely scrutinized. Thus, even if it decided to offer unlimited warranties in the UK, the outcry in the US and elsewhere would be very unpleasant.