This suggestion is for any Blaze mob who is touching soul fire to temporarily turn blue. While the blaze is blue, so are it's fireballs, and the fireball's particles are that of a soul fire flame instead of a normal flame. If a blue blaze's fireball strikes netherrack, it turns the netherrack into soul soil in addition to setting it on fire.
When a blue blaze is killed, it drops soul rods.
Besides being used as crafting ingredient (a blaze rod substitute), these rods can be placed in the world similarly to end rods; unlike an end rods, these are blue colored and their particle is similar to that produced when walking with soul speed enchanted boots on soul sand or soul soil.