since the forum reset ate my previous posting of this, im going to repost.
the idea is that one of the perks of retiring a character on single player would be letting the player pick a non-unique item they own, and causing it to become unique and adding it to the loot table for future characters. additionally to this, if they complete some sort of requirement (level, quest, difficulty, etc.) they could instead decide to pick several items and make a set (think diablo II sets or WoW sets) which could drop for future characters. or pick an item and beef it up and make it a super unique or something