Was Harvey Dent really needed in this movie?

Harvey Dent's inclusion always kind of confused me. What I mean is that, it seems logical that if he is going to be there, he is naturally going to be set up to become Two-Face in a later movie. But Billy Dee Williams has said that when he did Batman, he was only signed for one movie. Plus, Tim Burton was reluctant to do sequels until Warner Bros. gave him a large amount of creative control on Batman Returns. A likely by-product of that is that it wasn't a truly direct sequel (both story-wise, tonally and visually), and supporting characters like Harvey Dent (only Commissioner Gordon and Alfred were brought back) were dropped.

I always thought that you could've given Dent's dialogue to Gordon or vise versa and there wouldn't be that big of a difference. They're pretty much in the same spot as to show that there are others on the "right side of the law" (and there aren't totally corrupt officers like Eckhardt) besides a masked vigilante like Batman.