I'd say any horse is capable of a gait, whether they're naturally gaited or not. Some of the naturally gaited horses gait in the field and others you only ever see gait under saddle. When I first started riding gaited horses, the folks I was riding with explained to me that I needed to get the horse to collect, and then they'd get in their gait. That meant that I needed to give a little pressure with my legs and a little pressure in their mouth, not much, and that would put them in their gait. I wouldn't want to go trail riding with a horse that had to be constantly convinced to gait, but the trick works when you're training them or getting them in the groove. You could try that with your horse to see if he'll do it at all.