[Psientist]

Obviously adding a "hover" option to battlefield mechanics adds a level of complexity which is probably not worth it, but perhaps the current system wouldn't hurt a few tweaks such as the suggested coastline flying (so long as flying units don't end their movement on a water province) or trample-protection (not all tramplers even HAVE trunks!).

Some of the same could apply to underwater "flyers" if any still exist.