...if nothing goes wrong with anything in the system.
Don't get me wrong, I like EVs but there is always a risk that a single cell in the pack dies or a transistor on a BMS explodes and no one want to have anything to do with it. They will sell you a full pack which is usually so expensive it totals the car. This is a pretty shitty risk dangling over second hand vehicles especially.
Would be amazing. At the moment I don't know of a single brand opening up batteries to fix them. They all consider them a single replaceable component/module even though inside that's far from the case.