Necro time, adventures previews are out. TheOthin had the idea of opening inheritance/watchtower to give a turn 3 hand of 3 processions and watchtower, but this isn't quite enough. He also mentioned stonemason/inn/catacombs, but you can't quite cycle through all the junk on turn 2 or get a watchtower with your procession/procession/fortress.
Kingdom: Stonemason, Black Market, Develop, Watchtower (bane), Procession, Fortress, Catacombs, Haggler, x, y, z
Black Market Deck: Baker, Young Witch, bunch of other fun cards
Events: Borrow
Use shelters.
Turn 1 hand: 4 coppers, hovel. Play 4 coppers, borrow, use baker coin token, then buy stonemason, gaining fortress and procession on the overpay.
Turn 2 hand: 3 coppers, overgrown estate. Play 3 coppers, buy Watchtower
Turn 3 hand: Necropolis, (shuffle) Watchtower, Procession, Stonemason, Fortress.
Play Necropolis for 2 actions.
Play Stonemason on fortress for two develops, topdecking them with watchtower. 1 action left
Play Procession on fortress to draw these develops, trash fortress into hand, gain catacombs, trash catacombs, topdeck procession with watchtower. 4 actions left
Play Develop on fortress, gain watchtower on the deck, gain catacombs, trash catacombs, topdeck procession with watchtower. 3 actions left.
Play Develop on fortress, gain Black Market on the deck, gain catacombs, trash catacombs, topdeck procession with watchtower. 2 actions left.
Play Watchtower with only fortress in hand, drawing procession, black market, procession, watchtower, procession. 1 action left.
We now have a hand of 3 processions, Fortress, Watchtower, Black Market, and one action left. You probably know how it goes from here.
This is what I meant by you just needing one more little thing... what was stopping me last time was that on turn 2 I couldn't get a watchtower if I had gotten two 4s on turn 1. The borrow doesn't hurt because it just pushes the necropolis off to turn 3, which is fine. The first procession/fortress is clutch for getting the 4 actions needed for watchtower to do its thing. Unfortunately we have already trashed 3 catacombs and used one procession, but this should be alright given how awesome our hand is. It might be possible to do this even better, because there are plenty of other options for the first two turns.