Looking for help with a flier-based team.

Both Myrrh and Tana have the potential to be great tanks, Elincia doesn't have the best IVs but can still hot hard enough, and Azura is a dancer, enough said. I think there is potential there, though you'll need some SI for sure.

Elincia, Hinoka, Myrrh, and an Azura. Azura's IVs don't matter TOO much because her main roll is supportive. Providing buffs from Hone Fliers and being a singer.

There are some other units at 4*s that can also be good. The fliers don't have to be 5* exclusives to be good.

Est is an extremely strong flier with an attack boon, so she's really good with Brave Lance.

Florina, contrary to popular belief, is a really good mage-bait unit, although she's pretty expensive to build (Distant Counter) to make her into the best mage-bait that she can be.

Palla is pretty decent.

Caeda with her Wing Sword is good, but she still would want an attack boon.

Cherche of course.

Beruka is a really beefy physical tank.

Michalis is pretty good.

There are some others that I'm forgetting.

Don't you have any Cordelias?
She's an amazing 4* available flier.
https://imgur.com/a/bOapN

I've been building up a merged Cordelia for a while, and she's been amazing on both flying teams and mixed teams with her excellent offensive stats for a 4* available unit, with Hone Fliers support from NY Azura, she's very capable of both doubling and getting Heavy Blade activations off on a lot of common units (the most common reason for not being able to do so being that she one shot them instead of getting a second attack), and even if she can don't do one of those two things, NY Azura refreshing her allows her to proc galeforce on the next enemy she gets into combat with, either to continue the hyperaggressive onslaught or retreat back out of range.

Then for her teammates, NY Azura's an obvious inclusion, but Elincia is very useful for getting past enemy walls that Cordelia can't handle herself. Even with neutral attack, with Hone Fliers active, Elincia can generally deal with the greens that Cordelia can't, while TA NY Azura deals with the blues.

Then there''s the fourth slot, which is usually just an arena bonus unit with reposition to help Cordelia close the distance.

You can't really leave out the Grand Hero fliers though.
Michalis is incredibly tanky and, with Quick Riposte and Ignis/Dragon Fang, makes for a great physical tank.
Valter, on the other hand, is a tough duelist who gets kills often when he initiates combat, and he can take a hit if he needs to as well.