Well, I think it's cool that the MK team are finally getting to try making a fighter that's not Mortal Kombat, and they could do a lot worse than a DC licensed fighter.
I also think that after MK9, the team have much better direction in terms of the quality of games they make. What most interests me is the insinuation by the title and the teaser that the plot may be inspired by the Justice Lords (crux of the awesome story to the Justice League cartoon).
This could make for an excellent story mode at least. I don't really expect a competitive fighter from them anyway, but a cool solo one to play since they seem much better at that than the Soul Calibur team.
Oh and in terms of whom I want on the Roster, The Question is probably out (I can hope for a story mode cameo though), but Black Canary, Huntress and Green Arrow would be kickass.