I'm not sure the 3s were built with battery swaps in mind. I think the S (and maybe the X?) were. At one point in time, Elon's solution to 'charging as fast as a gas fill-up' was to battery swap your depleted battery for a fully charged one, then come back and get your battery at a later date... they abandoned that plan. I think they demoed the S being able to have a battery swapped in within 5 minutes. I feel like the 3 was not designed for that, and as such would take much more work to do. Given that the battery is the biggest cost of the car, and the large amount of manual labour I imagine it would take, why wouldn't you just buy an LR car to start off with? I don't think you're going to save any money buying an SR, keeping it for a few years, then trying to 'upgrade' to an LR... yes the LR battery cost will go down in 3 years' time, but the whole car's price will go down accordingly as well, so you'd probably be just as well off selling your SR and getting a 2023 LR.