The only problem is that neither mode of transportation can be controlled very well. Or rather, the Terror Form can only move in a single direction and has to jump and stop to change directions, while in the Destroyer Form all Gren can do is aim himself in the general direction of the enemy and attempt to glide/jump using the recoiling of his weapon. And like the Terror form, he'd have to use carefully measured stop/go movements if he wants to change direction or not crash into something (Unless that's the intent). And of course, he can always rely on rocket jumping if he only needs to vault himself to a position he can't climb (Which is very little thanks to his Friction Semblance).

One of his more favorite ambush tactics is to attack from the ceiling above his enemy.