If you do not want the loot then get someone to join a party that is up to P4S and effectively "elevator" your parties to P4S directly (at the cost of losing all the chests from 1-3). My group is doing this right now since the tier isn't going to unlock until nearly 6.2

All you'll need to do is once that person is at P4S, make them lead and they can start the duty.

Edit: Unless it unlocks in 6.18 as Lenneth said, I never really pay attention to exact patches.