Coin tokens in general are excellent in Double Tact engines, as they allow you to do stuff on Tact-playing turns that pays off later. CM and Plaza are the best for this. Baker, while very good, competes with other engine components at $5 and is often
worse than Plaza in Double Tact; Merchant Guild and Butcher are terminal and also $5.
The best comparisons for CM are probably Lighthouse, Squire, and Pawn, as all can function as cheap non-terminal Coppers. The others are probably better in general, as CM's +Buy is more or less useless in a Double Tact engine, but the flexibility could come in handy. Plaza, in a Double Tact engine, is basically a better, cheaper version of Bazaar, which is amazing. While neither of these two cards is enough to sustain a Double Tactician deck by itself, like Vault or Black Market are, both are excellent components in a more complex engine.
I don't have much else to say, honestly, because this is mostly a theorycrafting post; I noticed the synergy with Candlestick Maker in a game on Goko against -dg-. That game also featured Vault and me accidentally trashing a Tactician to his Bishop, so it's not the best example game. Have any of you guys noticed any other interactions with double Tactician and Guilds? We all know about the Herald thing by now, but I'm sure there's more to explore.