I’m a huge fan of many different genres. I also really happen to enjoy many of the gameplay elements of the the Borderlands franchise. That said, I thought how interesting the gameplay would be with a different game “skin” so to speak.
For example, I really like the Shadowrun tabletop game setting. Have Borderlands gameplay (RPG skill system, 4-8 classes/characters, loads of different guns, etc) within the Shadowrun universe (AKA: dark, polluted, dystopian Earth with fantasy races like Elves, Orcs, Trolls and magics like Shamanism, arcane magic, ki, etc along with advance tech, hacking, etc.)
Or perhaps a nifty “return of old mythological Panthons” type thing where you have classes pledged to different Deities/panthons whose skill trees are representations of their worship or something. It plays like a Borderlands game, except it has a different skin.
IDK, I just thought it was a fun idea and I was interested to hear what other people might thought might make for an interesting mixup. Maybe even pick other game franchises like Final Fantasy or a Old West style Borderlands or something. The power is yours! Let your imagination run wild!