Since it would have to be operated by the skill of the lowest common denominator, you could only have one person in a barrel at a given time. Otherwise, if you have 5 people in the barrel and one falls, the barrel will have to stop for that person to get up, lest they fall in perpetuity.
Which brings me back to operating the barrel. Surely you would have an operator for each barrel or two. Therefore, the staffing level is about 1:1, staff-to-guest. Impractically expensive.
The idea of skiing in a hamster wheel may sound ridiculous, but many a treadmill have been sold. That said, this particular idea should have been kept to the inventor's self until the obstacles like the above were better thought out.