I thought in the long halloween, a thug hands the acid to maroni, past the security check, and maroni throws the acid on dent......its been a while since i read it.
If the joker throws acid on harvey, ala maroni, then it means that the joker is a pawn for maroni, the joker can't be a pawn. If the joker gets maroni to throw acid on dent, i can live with that. the joker wants anarchy, he won't work for anyone, he gets them to work for him, and probably still kills those who work for him anyway. Why do you think he robbed a mob bank in the prologue?
The acid to Harvey's face shouldn't make him Two-Face, it should simply be the last straw, the icing on the cake, that makes the craziness and his double personality finally come out, besides the physical. His becoming two-face should be an on going mental struggle throughout, with many factors behind it, the acid is just the final blow that makes it come out. in a sense maroni didn't make harvey two face.......it was the corrupt society and pressure of being a da in that society that makes him two-face, the acid from maroni simply unleashes the beast.
The joker is "absolute" in the film, he shouldn't have a name or origin, it's better that way. Adds to the mystery factor of what he is and why he is ala batman #1.
This is all speculation of course, but how i feel things should and just might happen.

t: