Off the cuff plan to kill at least four five of 'em. Sorry if the plan is awful, I'm pretty rusty at this.
First, to identify probable kills:
Rider A @ 10 HP
Rider D @ 3 HP
Merc B @ 14 HP
Merc C @ 5 HP
Rider E @ 19 HP
Musings:
Sen and Chalco could team up to kill Merc B, assuming both land their shots as Gig said above.
Rider D and Merc C are at low enough health our melee should kill them to save our mages for the ones with higher health.
If we get a mage to smack Rider E, someone could potentially finish them off.
Rider A just needs a good smack with magic and that would do them in.
Vague(ish) Suggestions:
So far, it looks like Lizbeth could move (possibly try to hit up the northern houses? If she draws some pegasus, that just means they can't be here to bother us and she can move back until its safer to deal with the houses. She could also heal Odys if she wants) and Sen could take her spot to keep both safe(ish) and land a shot on the merc.
Chalco could finish said merc off then, as he suggested above.
Galen could move back and finish off Rider A while also being safe(er) from reprisal since he's at low HP
Lian could move down to finish off Merc C
Nicco or Titus could finish off Rider D, but I'm going to bet that Nicco probably has the far better hit chance. Either way, Nicco should move somewhere else with canto for Iolani.
Iolani could move to Nicco's old spot and nail Rider E from a safe distance. If she does at least 9 damage, Titus could move in to finish him off with a /far/ better hit chance thanks to E using a lance.
From there Vera could move in and heal some people (Cyrus or Galen would be my suggestion, Odys can sit on the ground for a while being a corpse wall since he's more inconvenient to reach)
Alice could... Do something? There's not much that comes to mind for what she could do at the moment, and no safe targets that I can see. Heal whoever Vera doesn't maybe? If so, then I suggest Vera heals Cyrus and Alice vulns Galen to maximize health gain.
Results:
If things go off well, that would be five less enemies for us to face with, most likely a level, and potentially avoid any counters. There's probably better choices for people to targets so call out if you think there are better, I haven't mathed anything out so I don't have specific percentages and am just sorta guessing likely hits.
This plan doesn't really address the fliers admittedly nor screen units away from them which would probably be a smart move but nothing is coming to me for now. I also admittedly didn't look around for any of us that has Daunt/Charisma, which I also should have probably done.