I had a friend offer me a 95kwh battery for my 60kwh when he upgraded his to 100kwh.
Tesla service said my suspension is not capable of properly handling the weight of the heavier battery and refused to do the swap.
Coil spring cars have different parts for the small/big batteries that were offered at the time.
The 100kwh pack was only ever offered with air suspension, so that’s a prerequisite to even getting Tesla to consider the idea.
There were also other considerations/complications when Tesla briefly offered the ability for P90D owners to upgrade to P100D. I’m not sure on the exact details as to why but they had to upgrade the SEATS from next-gens to premiums in order to maintain crash certification/homologation.
In short, I don’t think battery upgrades are ever going to be a big volume thing for Tesla. They have every reason to prefer just selling you a new car.