Having gotten OK's SSB but not BSB I still can't really decide if he gets a spot on my general A-Team outside of obvious situations like FF3 realms. My general all-around team ignoring any specific needs is usually the following (RW is Shout):
-Lightning using PC/FC and I have her Lightning SSB and Kaiser Shield
-Vaan with his BSB
-Tyro with SG and then FB and/or whatever I need for condition medals
-Rosa with her Medica/MBlink SSB
My 5th slot I kinda go back and forth on between Basch and Ramza; I have the Apocalypse Shield for Basch and can run BS/SC on him for good damage, but in all but the hardest/longest encounters they're over before I could get Apocalypse Shield up. For Ramza I don't have Shout but I do have his BSB (and Hail of Stones but w/e) which assuming the boss doesn't resist Holy is good damage and his first BSB comand also does good damage. So I can alternatively run FB + Life Siphon on Ramza which frees up Tyro for pure damage or whatever is needed. I tend to stick to Basch just for the more upfront damage but it's probably kind of a toss-up.
I also have BSB's for Gilgamesh, Beatrix, Squall, Noel and Ashe, but since I just got virtually all of those I haven't experimented with any of them really outside of Beatrix's. I don't think any of those would make my A-Team though except maybe Ashe if I ran OK BSB RW instead of Shout, but that doesn't seem worth it (again outside of specific situations that call for a mixed team like FF12 CM or something).
Vaan is a lock on my team with his BSB being so good (and the burst commands stacking with everything else), Tyro is also a lock as my only native Wall, and typically you'll need a healer so Rosa or whatever curaga medica is also a lock. So I could either swap OK in for Lightning as my PC/FC user (I'd lose the AoE SSB but that's not typically much of an issue), or I could swap him in for Basch but then I'd need to have him run something other than PC/FC, maybe Life Siphon and Gaia Cross or something?
Edit: Oh, OK can't use Knight abilities (aka SC/GC)? boooo. Hmm.