Making bare bones fireteam gameplay free-to-play is a good idea (not just to improve wait times, but as an advertising feature). You could have a ‘free hunt’ mode where players enter with only the basic classes or equipment. There would be more reason to have special guns in those weapon lockers so they can try them out.
If you added an option to select new classes at the reinforcement screen, then people would stick around after death to try out different strategies. Imagine free-to-play players being able to access Arnold’s class by being reinforced. There would be a lot less rage quitting, and an in-game system to advertise DLC characters that can be purchased.
Win-win.