I will open with saying this game is great, and it held my attention for as long as it did because of the story mode was a great way to get to know characters and explore the lore you worked to hard to create. (Plus if you play solo, you are the best player.)
At the end of story mode, the Battleborn state that they will always be vigilant and fight to the last man/woman/robot/monster/plant/animal/thing. With that ending I realized that this game NEEDS a survival/horde mode. The idea is very simple, pick a team of Battleborn (from 1 to 5 players) and go against ever stronger and larger waves of enemies. The longer you survive, the better loot and more experience you will receive. Personally I find this kind of game mode very enjoyable, and it even fits in with the lore of the game. You could even call it a continuation of the story.
Properly executed it would be a fantastic alternative to replaying the same story missions a million times when you do not feel like versing live opponents. A good PvE goes along way in my opinion.
Thank you for your time.