Blaze Powder in Fireworks.

Blaze powder could be added to fireworks in the firework  recipe. It would not replace the gunpowder. When blaze powder is added to a firework, that firework will gain a colorful trail, specified by a dye that is also added. The default color is fire particles. When put in a crossbow, the resulting explosion (and possibly also the trail) will light mobs on fire. This would not only buff the crossbow, but also look cool.