In fact it is possible to have other kind of troops throwing nafta bombs.
I wanted to try and have "uber" mounted crossbowmen, so i first wanted to change the bolt type since it affects accuracy.
But contrary to horse archers that can have the cav_bodkin_arrow there is no cav_steel_bolt or something like that.
So i used nafta bombs.
I'll paste the exact change i made, but i can assure you that these guys where launching bombs with their crossbows. (they are not throwing the bombs, the missile that comes out of the xbow is the bomb)