How to keep older playable characters fresh

The idea of adding in new vault hunters into BL3 is exciting to replay the game, but a great way to keep older characters getting the same love is by adding in some new skill trees, it would be a great way to keep people to also play there favorite characters, and has gives players some cool ways to re skill the tree. Example is for Fl4k, the robot could get 2 new pets, the Grog skill tree where it focus on Handling, and Accuracy, and the other one is a manta, which focus on Shields and the ability to summon ratches