Batteries are fine, the majority of the time it'll be in the pull stage as once depowered (the power is taken out of the kite by releasing the brake lines) you can bring the kite back down pretty quickly. Having two with the cycles staggered would reduce this but you need batteries anyway because you can't rely on demand being flat.
The algorithms to control the kite are pretty straightforward, the complexity to self launch would be a bit tough but it's easy enough for a human to do so there is no need to include that complexity for the use cases this is targeting. This wouldn't be a set and forget solution, not yet.
The kites will wear out relatively quickly but they're cheap to replace.
I consider myself a pretty skeptical / practical Engineer and I don't see any show stoppers, I think it'll fit the niche they're targeting quite nicely.