You can't do it mid-adventure because the build feature can change your race/class distribution, which maybe unfair. You are only allowed to change your team's gear. There's several we can fix this: - Make a party build only feature where you only change the gear and not the team: Too confusing and overlap with the other build feature - Let the normal feature load but prevent it if it load a build that change your party composition: Could be confusing but simple than the others - Disable mid adventure gear swapping altogether. You only get new stuff at the end of an advanture anyway. This makes much more sense. Cons: Change the balance of certain adventure and remove some flexibility in deck-building for specific maps - Enable full party change mid advanture: Same as above, easy to understand and simple. Cons: Confusing and hard to calculate EXP for participating members.