This might be hacky as heck and originally I wasn’t going to answer, but it kind of stuck in my head and I couldn’t help but thinking of any sort of solution.
I remember years ago when I was first learning UE I made a ridiculous “flying pawn” that was just a regular walking pawn. If i remember correctly I used a tall volume and measured the actor’s location on the Z axis within the volume.
I then would move the skeletal mesh higher up on the Z axis when the volume overlapped with another object. I think I used sockets on the meshes to get the top most height of the object. With some blendspaces you could do some cool stuff with it.
Also as far as the collision issue goes, say for example you use a standard pawn and not a flying one, you could set the collision to the sapsule component to ignore everything but the terrain, but then change the collision to block whatever you need to on an additional capsule you can attach to your skeletal mesh. So the character can move around freely, but will collide in the air with objects if say perhaps it doesn’t get above it quickly enough.
While that might not help you at all, maybe it can help get you onto another train of thought