Okay, I still don't see a major problem with Laguz. There is a clear mechanic to how the gauges work, and it'd be easy enough to figure that out for a battle. It's not like this is anything more complex than, say, Mitsuo the Hero or the multitude of SRPGs with movement-based attacks.
Anyways, for characters: (Stealing Ciato's list and editing, since that looks mostly like mine)
PCs
Support: Micaiah, Sothe, Elincia, Nailah, Caineghis, Sanaki, Kieran, Marcia
Maybe: Haar, Volug, Geoffrey, Lucia, Nolan, Kurthnaga
No: Everyone else.
Bosses
Support: Zelgius, Sephiran, Lekain, Izuka, Jarod, Oliver, Dheginsea
No: Everyone else.
Right. Like I said, I don't see the trouble with Laguz, which means that there's no real trouble with Kurthnaga (and, at endgame, that wouldn't be a problem anyways, as much as it doesn't represent his in-game style for most of the game). Dheginsea, I'd be totally in support of, since he's an interesting and damn powerful FE boss. Ashera, I'm gonna have to say no, just because that would entail the shield things as well, and those + the AoE effects make her damn annoying to interpret (would an ST character need to take 8 turns to break all shields? Would the number be scaled considering PCs? This is where Tal interps help.)
Undecided on Geoffrey and Lucia since they have little-to-no gameplay presence outside of about half a chapter, are not memorable at all and are useless end-game. Volug and Haar are more interesting and better for gameplay, but have very little plot and are incredibly dull in the DL, unless I'm forgetting some weapon Haar lays claim to. (And I'd hold Volug to Halfshift in the DL, even if he's better without it)
Nolan is an odd one. It seems good to have a DBer in there, since they're forced and thus have a gameplay presence, and Nolan is by far the most useful one at endgame. He's also different to, at least, Boyd, who is the only other Tellius axeman we have, in that Nolan is not a glass cannon. Leaning no here, unlike the previous 4, but could definitely be argued.