If they can't provide service I'll be going to other brands that's have a larger service network.
The app does a pretty poor job of not allowing you to specify issues outside of the standard flow. I could have called a service center but between how hard it was to source a 12v battery independently(I know it's a deep-cycle battery but still!) and high mileage I just don't think it's a car for us any more.
One thing to note though is that not all repairs are mobile serviceable. For example, when my Model 3 needed its front control arm replaced part of that service involves doing an alignment. The Mobile Techs aren't going to be able to do that one.
Shouldn't have to replace it for a long time (if ever) and seems to work fine. More expensive than lead acid but more convenient than service appointment for a 12v battery.