you're going to have to find an independent builder if you want a fully custom rig that you don't build yourself. When I build a system it's in full consult with the person for whom I'm building it, and every system is 100% custom.. right down to the paintjob and lighting effects. The larger companies don't generally do that much custom work.
(no, this is not a solicitation, because my plate is full already and I don't have time to build you or anyone else a computer. And even if I did I certainly would not solicit that business here
)