I think, the appropriate course of action would be to recognize Philippines as part of the Chinese "co-prosperity" sphere. Who cares about the wretched place? Let the Chinese bother about it.
I actually think Duterte would be okay with that. It'd give a closer semblance to the Philippine sovereignty espoused by the left and the political wings he supposedly associated with when he was younger. The rest of the Pilipinos probably wouldn't be.
Do you think the Chinese would keep him? I strongly doubt.
If you mean by keeping him, allowing him to remain in power beyond his term, no, but I don't actually think he's interested in that. He seems to be a person who truly believes in his ideology, and would step down if his term ended. As long as China gets their islands I'm sure they don't mind working with Duterte for six years.
I mean, keeping him as the first secretary of the party committee for the Pilipino Autonomous District of the PRC
