Hmm so basically you want items to hang in limbo until you either need, greed or pass on them at the end of the dungeon when the drop you wanted doesn't drop. But as the guy above is saying, people will troll the snot out of that, either to keep others from dropping party, or just to see the reactions. Personally I think it's best to make do with how it's set up now. If you want something else, just run again afterward and snag it then.
Or if you're talking about stopping the loot timer if no one needs or greeds on it, that's a little bit unrealistic. If it's sought after, someone always will.