Gotham Knights: 10 Reasons To Be Excited
2. New Characters & Costumes
During the gameplay reveals Batgirl was liaising with characters such as Alfred Pennyworth, the late Bruce Waynes butler and adviser, and Renee Montoya aka The Question who both provided in game narrative assistance in a similar manner to how Alfred or Oracle would aid Batman in the Arkham games.
Another feature is that during the cinematic trailer, Tim Drake is shown wearing a classic Robin costume, similar to what Damian Wayne wears in the comics, whereas during the gameplay trailer he is seen wearing a classic Red Robin costume. This would indicate there are a variety of costumes on hand for the player to unlock.
With DC's long comic history there will hopefully be many more costumes and equipment available such as Nightwing's classic outfit as opposed to his New52 look, or Kate Kane's Batwoman look for Batgirl (unless she appears as a playable character herself), maybe even Jason Todd's outfit from the Arkham Knight could make an appearance, continuity aside.
How this will factor into the game we do not know, as it could be merely cosmetic or feature bonuses such as how apparel in Breath of the Wild had perks when wearing sets.