Watch this at 7:50 - Solo has 3 AI. If you play 2 or 3 co-op, no AI - https://www.youtube.com/watch?v=vmuPlWdDB9c
It's the best way to do it, Gumby. Also, I love that user name
I'm a solo/co-op player, I regularly play with a group of folks I know. According to Ubi the game also scales based on the number of co-op players, so it should be tough, but fair in that regard. You will also be able to play on your difficulty whilst your friend plays on theirs. So you want to play on Ghost and they want to play on Easy, you can do that.