Using an external core for gamestate management

Hi everyone,

We are currently building a fairly complex card game in unity complete with an artificial intelligence opponent. In order to test the AI we built a command line version of the complete game and built and tested the AI against those core mechanics. We are happy with the decisions it's making and we are now looking to move everything into Unity. My question is are we better off starting from scratch inside unity or just interfacing with the core we already have? Does anyone have any experience with external gamestate managers and/or how would something like the MVC model work in an engine like Unity?

Any advice, stories about success or failures doing this, or opinions are welcome. Thank you in advance!

 

What's the command line AI written in?