I was considering doing this with my Yamaha Recording Custom kit. The main kick I use is 20x18 and it sounds good, but sometimes you want a different sound. The only con I can think of is that I imagine the build quality of the marching bass drums are usually less than drum kit drums, but other than that I think it's a really smart purchase. You get an extra kick, usually the prices are fair, and a lot of the time depending on the brand you use you can find a matching drum to fit your kit. For example I found a type of Yamaha marching bass that uses the same exact lugs as my kit, and the same color so it's a perfect match. As for spurs, I agree with Gruntersdad that the hoop mounted spurs might loosen eventually, but the spurs used by maxcolumbus look like they are really high quality. By the way, that kit is beautiful, I'm jealous.