Maybe, but the FAQ states the current battery isn't replaceable. So it seems more likely they'd have to come out with an entire new unit in order to have external batteries.
It doesn't seem like something they're interested in for the launch.
Since they're using the upfront pre-order money to cover manufacturing costs, I would bet enough feedback from customers (or even speculative customers) asking for a 30 min minimum would have enough impact for them to source different batteries or reduce weight. Features like this can make or break a flashy new product like Lily.
It doesn't seem like something they're interested in for the launch.