My preferred grip is the CAA (though the FDE does not match Magpul or Vltor). I'm stuck with the MMG on the featureless.
I do like the Magpul enhanced trigger guard (and prefer it screwed in place, not pinned).
For buttstocks, I've got a basic A2 on my featureless build, a Vltor Modstock on my 14.5", and an RRA Operator CAR on the AR-22. The Modstock and Operator have storage for spare batteries.
For handguards, again, I don't care for the MOE and instead run the Troy Battlerails on the 14.5 and AR-22, with stub rails on the 6:00, 9:00, and 3:00 only where needed or at the front out of the way, so I've got a nice, smooth tube to grip that doesn't feel like I'm shooting a cheesegrater.
Yes, the MBUS are just backups and I understand that. I prefer the Troy BUIS.. but yes, I do have the MBUS on my 14.5"