Gaited horses are wonderful. But it is almost a sin to try to "ungait" one, in my humble opinion.
It's like taking a TB and asking it to do draft work, or taking a QH and asking it to "gait."
It would be better for you and the horse to just get the right horse for the job to begin with.
Puttzing around with barrels or games is different. But if you want to actually compete, please don't buy a gaited horse and try to ungait it.
My friend bought a Fox Trotter they tried to make a rope horse out of. I have no idea why, she wasn't even built anything like a stock horse (some of them are, but this one wasn't). Needless to say that horse didn't work out for that purpose and my friend bought a lovely Fox Trotter for trail riding cheap.......wish I had gotten to her first!