It sucks that Ouki didn't think of this conversation when he was about to die and pass on his glaive to Shin. It would've been cool to see this after 100s of chapters later.
But still, people always look and refer to Ouki's glaive that Shin is the one who inherited it but it's a symbol of his will and dream. Ouki wanted to see China finally united and when he was about to die, this glaive was taking a part of him in hopes that his dream will be carried out by Shin.