I love CO and suggest you go with them. I have two observations.
1. Full Fare customers go ahead of any type of elite if a seat opens up. This is as is should be.

2. CO always holds at least 2 FC seats on all flights until the day of departure for Full Fare paying customers. They are supposed to be released 2 hours before the flight, but it can be anytime from 12 midnight(or 1 am) of the day fo the flight. This is unpredictable. However, if you have access to ITN, you can see at all times which CO flights have FC seats available and the number. You could tinker with your itinerary to reserve one of the flights with open FC seats. If you pay FC, you will get one of these.