RTF is a global modification that replaces all towns in the game.

Increasing the speed of flying units could increase the demand for spells like Fireball, Crystal, and Wall of Swords; this would be interesting, but the number of elementals would have to be reduced, as it would be too powerful to have 2 flying units and a caster at the start.

It's not necessary to increase the speed of all flying units to the maximum; I was only suggesting giving a higher speed to those units that teleport (and perhaps a couple of particularly light flying units – if all flying units have high speed, it will reduce diversity).