I've gambled on Tr/Swindler before playing 3rd player where the other two opened Ghost ship. Odds of me pairing up those two thanks to a Gship were pretty high and I had very good odds of giving out some curses. With a few Council rooms ahead of me in purchase, I could see opening Tr as well.
I could see doing something similar with Procession, particularly something like Squire/Familiar or Goons - or Market square/shelters out. You need just two additional cards to have good odds of hitting the strong play - and when you are down against 5/2 in 3er or 4er, well risks need to be taken.
I could also see opening Tr or Prssn with Noble Brigand setting up 4/4 hands and some odds improvement from something like Gship or Cr.
Outpost can work with several shots for 5/2 openings. Peddler setups with non-terminal 2's are pretty good for opening Opost. For instance, I've done Chap/Outpost/Haven/Peddler. Fool's gold is quite strong, effectively giving your double Fg AND cycling a bit when you play Opost. Opost/Chap transitions really well into Poor house setups - you can buy Phou's during the Opost turns and with some village/draw/+buy you can just roll out a quick engine that may well hit even on the Opost turns.
Opening Duke? Maybe, just maybe something like 4'er and you see P1 open Nb (you discard 2 estates), P2 opens Island, and P3 opens Duchy. This could then set you up to get Duke/Trade route with starting 3 coin Trade routes. I think if we did the logical extension of 6er with Tunnel and Greathall, we'd really want to just go double Trdrte.
Curse: P1 opens Nb. P2 buys an Embargo (had a 2/5). You buy Trader. P2 embargoes curses (buying Trader as his 5 was turned into a 4). Your next hand is Necro/Hovel/C/C/Trader and you buy a curse, revealing Trader twice for two silvers.
Scout: Open Nomad camp on a board with no villages, but really strong non-terminal 5's (e.g. Stables, Market, Minion) with non-terminal +buy and Peddlers.
Villages, of any type, can be the correct opening in 4'er with some really strong simple engine (e.g. Goons/Menage/Chap) where a run on villages will really limit your ability build the powerful deck (if you have 3 villages then you can run 2-3 goons with a terminal trasher for big points).