> Perhaps the body shop is better at taking care of conventional cars and lead acid batteries, and just needs a little experience and education about lithium-ion systems?

Lithium-ion batteries are much less subject to drain over time if they're not being used.

The Model S uses a 12V lead-acid battery though(and subject to the drain and upkeep you mentioned), so I'm not sure why they author has been waiting on this bespoke, single manufacturer one. Unless maybe the connectors are non-standard?