This is something that I have been working on. Try this.
In a 2 player game, always treat the coffers as another player as well. This would allow the Counterfeiter to steal 1 from an opponent and one from the coffers. I also would assume the coffers always has 1 team in play (for the dirty cop).
This may improve your experience. Please let me know how this goes.
I was also trying to make it different to the Con Man but I guess it can't be helped too much in order to implement a solution for the game as a whole. This definitely sounds like a good overall solution. I'll give this a go and let you know if I find anything particularly unbalanced with it.