Simple, it'd require new melee mechanics built from the flight system of Swooping Hawks, and that in return would require new animations, something that can't really. Also, there's little to no air-based melee avenue in Eternal Crusade. Considering how jump packs work for the other three races, you're not going to see any exhilarating aerial melee fights. Even if you did, they'd just get shot down in a matter of attoseconds. Not all too exhilarating now, eh?