I'm not sure what arts you're talking about mixing here, but I think I'd be worried about the exposure factor. I was never a professional, I just learned from and sparred with an 8th degree friend of mine. A snap or roundhouse kick delivered in the right (or is that wrong?) way could show off your pride in a way you don't want. I've been to unhealthy to practice any arts for about eight or nine years now, but I don't think I'd have sparred in the kilt without something underneath it.