That's badass, but people who want badass PCs tend to be the ones either buying them completely as-is, or building it by themselves. People who build them solo are looking for the best value for the best product. Having a special proprietary case is just going to add cost where those consumers are never willing to accept it. I don't know if the remaining market is large enough to support this kind of swap-ready, high-end, high-expense technology.