I talked with Mike last week.
From what I understood, he'll still be in communication with (consulting with?) the Big E guys, but the actual building of the cabs and all of the business stuff will be through them -- there will be, IIRC, a Bodai 112, Bodai 28, MAS 28, and MAS 18s in the line.
The 5"-based cabs (the "tower" and "box" 45s mentioned in the big thread on the EB side and on the MAS Facebook page) won't, from what I understood, be in the standard line produced by the Big E guys, but Mike will build a few himself here and there. He said that, while the 45s (the tower version, in particular) are his current faves for his personal use, they cost more and take up more space for a given output volume than the 8s do and were, thus, less practical for inclusion in a regular line (which I get the feeling he and the Big E guys both want to slim-down and standardize).
This could change, of course, and I don't speak for Mike or the Big E guys.
Coming back to the 8s, I was considering a 45 but, after talking with Mike, am inclined toward a pair of 18s, which would see use with electric and maybe, on occasion, amplified cello. It sounded like the 5s (per Mike, more hi-fi) would have an edge for cello but that the 8s would still be good and, with electric bass, more practical (louder as a pair, smaller as a single, and probably voiced more in-line with my preferences on EB).