The huge cavity is there for versatility. For example, Aristides guitars often come with Fishman Fluence active pickups including the USB rechargeable battery pack. That will all fit in there.
You can specify colors and such but the shape that comes out of the mall is set. Soapbar P90s is simply not an option for this model. They have different models that can be fitted with single coils.
Here are some factory pics of the work in progress.
