I've often thought about suggesting playing this expansion with my other half (whom happens to be my main gaming partner), as we've played the base game loads competitively. Now she's not into solo gaming but I've played this solo a fair few times, and I really enjoyed the experience of some of the longer scenarios and would love to explore and share them with my other half. The best way I can think on handling game play is to naturally approach it as a co-op, with discussions on what to do but taking turns (round by round) to make the final decision on what we do that round.
btw my favourite solo scenario (forgotten its title) is the one that triggers end once all the exploration tiles are out and you score gold if you have no unemployed locals. It takes me a good 3 plus hours,but what fun it is.
How do you two like the game as a two player?