Consistency in cutscenes. The artstyle really didn't mesh with the rest of it.
Also, the story was laughably bad. So hire new scriptwriters, and try and distance as much from the first game as possible, story wise. Faith was boring as hell, so make her less boring, or just get someone else.
No gun combat. Melee combat could work; perhaps a small extendible baton you can carry around, to decisively deal with enemies in your path quickly, but easily overwhelmable with more than 2. It should be more about moving forward and fighting as little as possible.
NO cramped spaces, and far less interior levels in general, which rarely worked.
Free roam city would be sweet, but more open ended missions in general would be fine instead. Multiple pathways, entry points, that sort of thing. Would really make thinking through a path much more useful.
Oh, and fix the godawful screen tearing.
That's about it though, I quite enjoyed the first game, despite its faults.