The biggest synergy here is with Countinghouse. A non-terminal that lets you save coins for a later turn that lets you pound copper and then actually get more than 6 VP on a Chouse turn. Csm is one of the best Chouse enablers out there. In theory it should also be good with Pstone for similar reasons, but the one time I tried it I was less than impressed as smoothing is not as valuable with the potions cost.
Csm is also a decent workhorse for several other alt-VP runs: Duke, Silk Road, and Vineyards all like CSM. The former work well with large swathes of copper and smoothing while the latter like non-terminal +buy. This is one of the places where I would open with doubles - something really boring with Alt-VP I plan to copper flood.
Menage is another of the limited draw that really likes Csm; in general Csm is one of the most cost effective non-terminal cash options in the game. It is 20% cheaper per coin than Festival; the ability to precisely target price points likely makes it another 20-30% more efficient and of course a lot of boards can easily mass Csm where festival is outside of the price point. Yeah it is nowhere near as space efficient and lacks the +action, but if you have reliable draw (and Menage is really good for that) you may want to go Csm over Festival. While Sqr and Pawn are more versatile, they are less able to mass both $ and buys for things like piling estates. Minion similarly likes Csm, though Minion games tend to care less about cost efficiency for building buying power.
Another fun Csm option (shared by a lot of coin token cards) is the fun of Mission multiplication. Paying $4 now to a whole second run through your Csm tokens can be very effective for building cash value. Rarely, banking tokens can quickly let you build a megaturn without gumming your engine. Something like Menage/Opost/Csm/Mission can allow you to triple play each Csm, over two turns each Csm can get to $5 and easily haul in a huge amount of VP in one final go. What makes Csm better at this multiplication is that it needs only draw to work; Merchant guild does not work on Mission turns, Butcher needs +action and draw while Plaza & Baker typically needs +buy when you cash out and often a bit of draw help as well - not to mention that Csm is much cheaper to mass than all the other options.
A particularly fun shot with massing Csm & banking coin tokens on a Mission turn is that you can push an opponent who lacks the gains to green much sooner than they otherwise would - you can threaten 10 gains a turn and have a pile of tokens ready to spend after the Mission turn. If their deck whiffs for a turn, you can instantly pounce to game end so they may be forced to green early out of fear.
Yeah 90% of the time, Csm is a non-terminal +buy with some smoothing that you want in the second to fifth shuffle. But even something as simple as this card has a few tricks up his sleeve.