You might be hoping for a long time, as unfortunately the Rainbow Six franchise hasn't exactly been all that realistic since Raven Shield (which was 8 years ago.) The series has been action-oriented for a long time ago now, and there's been no indication that this trend would change - much to my disappointment.
I think Vegas has the best coop in the RS series.
I also like RS, RS:RS and RS3 since they have the mission planner. Real real tactical simulator game.