Hawkman looks BAD-ASS.
Of course, it will bare unwelcome comparisons to JLU's "Shadow of the Hawk", which introduced Hawkman to the Timmverse in a team up that included Batman and Shadow-Thief. HOWEVER, that episode of JLU was hardly it's best, bogged down with some conveluted stuff. THE BATMAN's version of Hawkman can be purer and simpler, which can be good or bad, considering how it is depected.
In some ways, Hawkman could be interesting. Like Batman, he seeks to uphold the rule of law, whether on Thanagar or Earth. Unlike most aliens, though, he doesn't have any true "super powers", if they go by the iconic version. The mace, the wings, the gravity-belt...all technology combined with skill. So, if played that way, Hawkman has much in common with Batman. Of course, played as many of the JL team-up's have been, Hawkman will be a winged hero with a mace who teams up with Batman for 22 minutes to fight people, no more, no less.
He is an interesting choice as Hawkman is hardly popular or even rumored to be cast in ANY motion picture version of JLA. I'd have probably preferred Wonder Woman, Zatanna, or Black Canary on the JL roster instead in THE BATMAN. But it could be decent. Black Mask has usually been handled well, and the animators hopefully will have a field day with Shadow-Thief.