Well since fireworks actually explode, why not make them as possible weapons. What if when fireworks explode, they deal about 2.5 hearts of damage, and have a 55% chance to set mobs on fire, or when the large fireworks explode(add fire charge) it will deal 3.5 hearts of damage and have a 75% chance of setting mobs on fire. Possible uses?
Well, it can be used as a quick alternative to attacking mobs underground, since the rocket will get stuck on the ceiling. However, it is not limited to underground as one can simply set the firework off under a block controlled by a sticky piston, then as it is about to explode, the piston can remove the block blocking it and let the rocket move slightly higher to explode at ground level, making great concealed surface traps, though quite expensive. And the best part? It does not destroy terrain. Too OP?
Well, it is not as it is actually quite expensive, and that it can also harm yourself easily.