Herbalist-PStone IS pretty strong. Of course, so is Fishing Village/Merchant Ship (totally ignore gold, I don't think trader is any good either), probably not preferring KC to Province ever. Herbalist/PStone also potentially has access to possession here. I'd guess it's got to be one of these two strategies, though.
Rats/Trader seems like a really bad plan - it mostly just seems very slow, as it's turns to get the rats, then turns to turn them into silvers, and then you get the silvers and can buy stuff. I actually suspect straight BM is better.