Looking at both of mine without opening the Series 1 I can say there would be some routing required on the BB. On both basses the control cavity covers are the same size and location. This half is semi-hollow from everything I can see but there is a crossmember at the top side of the cavity. A cursory look inside the BB cavity tells me I would need to move the LED switch to add the XLR connector. For the side where the preamp would reside the cover for my BB LED battery compartment is smaller. I cannot tell if this side is semi-hollow as it is surrounded by wood. Without measuring I would say the LED battery compartment would need to be lengthened a 1/2 inch to inch to fit a preamp. Then, if desired, you would need to route a preamp battery compartment in the tail of the neck. I'm not sure how to handle the hum canceler as the standard pickup locations don't allow a front mounted one. Since it doesn't have to be in between the pickups I'm sure a place can be found for it.
None of this is something I would consider doing myself but I don't think it would be that complicated for Alembic to do in their shop.