What if the place that would be the worst nightmare is somewhere back home... and canonically it's been proven the character won't crack or go insane from being trapped there.

See, his worst nightmare would be if he found himself back on the broken Rumbar Pirate ship, the place he spent 50 years alone. However, there's really no way to make him snap cause... Brook just doesn't mentally snap o_O Would I then be able to have some sort other condition for him to be sent back?