It going be vague suggestion but the idea is separate map with a vault with Tina and Ava task in finding a vault and the DLC ends with the revival of maya without her powers and Roland but the power of vault collapsing and you have to escape.
The reason I chose the two is I chose the two is their strong connection to dead character Roland and Maya
More time with Vaughn, Tina, Brick, Birdman, other VH (side missions, events, etc.)
More of ability to alter my room and ship
More trophies appear on Sanctuary like list of location phoenix channel is access, part of target in zero room instead cross out picture, a trophy room for achievements similar to hammerlock room: mannique with your favorite outfit, memorial for the fallen like Scooter, more places show off weapons, achievements statues or objects .