While Kanki seems more loyal to Qin than Ousen, giving him the right to freely wage war doesn't seem like such a good idea.
The sixth Great General could go 4 ways: 1) An actual, proper person like the strategist guy; 2) Heki for the lolz; 3) The idea from the comments that he will appoint a sculpture, which would be either a symbol of absolute loyalty or a stand-in for Shin; 4) Ei Sei appointing himself. I'm not sure what benefits that would give him, but still it would have been funny.