Tesla has tackled most of the concerns people have with EVs but battery lifetime is still a concern for most. Therefore, wouldn't it be great if Tesla can give a guaranteed future replacement cost for the battery after of (say) 5 years of warranty - irrespective of condition of battery. What this will do is immediately increase resale prices of all Teslas and that in turn will tempt new buyers. I am sure Tesla can quite accurately work out what a battery would cost in 5 years time so for example, at the time when Model 3 becomes available, if Tesla can give a guarantee that at the end of its battery warranty, we have the option of replacing it with a new one for say $5000 (Model 3 base pack price in 2024) and that will come with another 8 year warranty, then EVs are really going to take off. We will also see used Teslas with battery replaced coming with a warranty. Of course the remainder of the car might be out of warranty but that again is a huge opportunity Tesla have against ICE competition that not a lot can go wrong, so coming up with a clever maintenance plan with a guarantee can make a big impact. But they will have to get the basics right in the first place i.e. reliability and build quality will have to be up there with the best. I reality, I can appreciate the costing side of things might not be quite so straight forward but I can guarantee this will convince a lot of the remaining EV skeptics that a Tesla EV is indeed a very good choice whether buying new or used - this will be vital if Tesla wants to be in the list of top sellers overall, not just EV.