Posted this in the other thread:
I see him as maybe a young, honest cop on the force who catches on to the fact that Gordon and Bats are in cahoots. Perhaps he was once one of the few cop believers in Bats, and now faces the dilemma of trusting him. His small character arc can tie into themes of choosing what to believe for yourself, and faith.
"Sometimes, people deserve to have their faith rewarded." I could see an honest character serving as an outlet for such a theme/plot point.
Or, I could definitely envision him as a young hotshot Assistant DA/someone involved in Gotham's law department, who has Gordon's nuts in a vice over catching Batman. He may not be the highest ranking member of the food chain, but perhaps a young, arrogant prick who thinks he knows everything about Gotham and how to fix it. Of course, he'll get some comeuppance at one point or another, either at the hands of a terrifying Batman, or a villain.