You only want three people anyway. One driver, one observer and someone at the business end of the rope. Even with a tower, you really don't want people in the back blocking the view of the observer.
To solve the people carrying capacity, get an old pontoon boat and convert it into a party barge. Even a little 20hp motor would be good enough to put put out to the ski area with the entire Swedish Bikini team. Use the ski boat for boarding and beer runs.
-Mark