The mixed Uns are mostly to give more variety in my minis collection. Also, running pure Uns all the time makes me feel...cheap, somehow, like I'm talking the easy way out in my force building. Irrational, but there it is.
I was planning to stick with standard Boggarts most of the time, with the Roc meant as an escort. The Centaurs are a pure group because I really like the Centaur mini and the only other Proto-using faction I play does not get access to any Centaurs, and the Basilisks are by themselves because I'm kitbashing them as B-Q-Bs, and I don't really see those working that well with other types.
The Arrows are indeed field arty, which means only five shots per launcher. As such, I figure three TAGs is enough, four if I include the Cephalus in the mech Sept. I'm usually a bigger fan of unguided rounds and splash damage, anyway.
The Heimdall is a bit weird, but I included it for two reasons. 1, it's on the WoR RAT, and 2, I happened to own the mini and wasn't using it for anything else. All else fails, I could say my cell is part of Etienne Balzac's group down in the Falcon OZ. Much more believable that he'd be able to get ahold of a WiE machine somehow.