A time machine that teleports you and your entire party towards a specific time. It would be like teleporting you to a past event in the Bleach Main Storyline(or filler >.<) to relive what happened before. It would be like a dungeon and you'd have to fight or do something like the bleach characters did. Example: Ichigo versus his inner hollow when hes trying to get hollow powers. At first it shows Ichigo getting owned then you and your party comes out of nowhere to help. After you help him defeat it you get a reward, exp, loot, and get teleported out. Also, when selecting the time/dungeon you get to choose the difficulty and it should show the recommended amount of level for soloing, or lets say having 3 in a party. (difficulty,loot,and reward changing also on the amount of players).
Although, this is kinda a big suggestion, it's more of a future suggestion or for you to do it little by little(lets say just adding 1 boss fight, or a part where u have to run(lets say going to soul society for the first time)).