I mainly think of one mod : Misty worlds, or rather the way the terrain is made.
(a link for those not knowing what mod it is : https://modrinth.com/mod/misty-world/gallery)
Having floating islands is cool, but there is either a void (that is a quick death) or ocean (no death and no punishment) if you ever fall from floating islands...
But having highly elevated terrain with a toxic fog, even better if the fog can go up and down (maybe more than in the good old misty world), could be awesome and make aeronautics the "only" way to go mining and escape before the fog rises.
I've seen a mod "rising toxicity" but still prefer the old way Misty world made the fog toxic.
Any thoughts ? Anyone able to revive the mechanic ?
I'm an amateur pixel artist and now some if anyone wanna work on that.
Also, having big slow flying creature fights in the sky would be soooo cool, like "whale hunts". Lots of fictions did have that, including an anime in the last few years, but I cannot find the name back...
Well, anyway, I just wanted to vomit some hope while making an aeronautics modpack.