Well to give this thread some input those are the power ups / improvements that I think the Gremory team might have ... sometime after the events of volume 17:
Rias - decreasing the time needed to prepare her Extinguishing Star ... along with using it's attraction properties as a defensive measure against incoming ... long distanced ranged attacks.
Asia - gaining a sub spices Balance Breaker that will have some offensive and defensive abilities, which will decrease her dependency on the Pantsu Dragon
Akeno - using her Fallen Angel mode without the bracelet that Azazel has given her ... along with some improvements to her Lightning Dragon ability, where it will be capable of containing some more elements then just Lightning.
Koneko - increasing the length of Shirone mode + learning a few more Nekomata abilities.
Kiba - learning how to use Gram without a risk to his life
Xenovia - learning and mastering all of the Ex-Durandal related abilities
Gasper - improving the length of his Balor mode + learning a few more Balor related abilities
Rossweisse -
Ise - decreasing the stamina consumption of his Sacred Gear related abilities and learning how to use his dormant Great Red / Ophis mixed power.