I (along with A LOT of other players would like you to reconsider doing a release entire box option. I currently have 2 boxes full of abras. I don't want to go through each one of them clicking "release" that'd take too long. If the worry is about accidentally deleting an important box, have it be a triple confirmation. letting them know how many pokemon they're gonna get rid of each time.
ex: *clicks release all in box* popup "are you sure you want to release this entire box?" yes "You will be getting rid of ## pokemon. is this ok?" yes "please look through this box one last time to make sure you aren't going to lose anything important. Delete?" yes *all pokemon in box get deleted*