That is a horrible houserule.
1. Casters are far more likely to be flying than non-casters, due to having far more options for it.
2. Flight is already FREAKING AMAZING!
3. Most people would say that it is the MARTIAL classes, if anyone, who should be best at tactical mobility, avoidinf AoOs, etc... (I realize this is patently untrue in Pathfailure, but that's because it's the caster love-love edition, no need to exacerbate the problem)
--> 3. a. The casters can already teleport and such already anyway
Ergo, by the above, your houserule idea sucks. If I were your player, and you broke out that idea to me, I'd actually get upset at you for it.
Mod Note: See my post below ~Umbran