I like this idea. But maybe you can mix any other ash from a fire with a Protector's ash. Maybe you just needed a small amount of Protector ash mixed in. Otherwise, jeez, you would never have enough.
Jacob's ash seemed white in color, while the ash they've been using as protection was dark - either grey or black. Not sure if that means anything.....
Could be... but Jacob's been on the island for a LONG time, who was there before him? This would mean he's really not the man behind it all, as it were, but merely carrying the torch. It might also indicate that the MIB has been on the island much longer than him?
If the white ash is the remains of Jacob's body, perhaps the black ash used to repel Smokey was the remains of MIB's body. It seems like MIB lost his original physical form at some point.
It's really really bugging me!! MIB kicked him into the fire, then seemingly a few minutes later the fire was completely empty. Now it's chock full o' ashes? Not possible. Bodies do not burn that completely in a CAMP FIRE, in MINUTES. Not possible! And I'm not sure, but it seems like he left behind way too many ashes. The whole thing just bugs me.