It won't be a 'burden' unless the money prize is too low or they set the time for the matches inappropriately.

An UEFA Cup / Europa League type of competition will give other users the opportunity to win something; it will also encourage some users after they came 3rd in the group stages and got knocked out of the Champions League. Also, it will make the group stages more competitive as the two bottom teams will fight for the 3rd place rather than giving up and playing with reserves.