I would not have done it on separate tickets but (unless it is absolutely vital for you to get on that PVG flight), I would risk on a single ticket and let them sort out the reroute things take an unwelcome turn (it is AF's responsibility to reroute you if you are on a through-ticket).
On the day, I would play it by ear:
1) If I am not mistaken, From MPL, I think that the CDG flights leave after the ORY flights for connection to the PVG flights. So, if it looks like the ORY flight is going to be delayed, I would ask AF whether I could be transferred onto the MPL flight pointing out the fact that I am going to miss the connection otherwise.
2) If it looks like it is going to be OK but the flight nonetheless gets somewhat delayed, I would consider getting a taxi from ORY to CDG.
3) If the MPL flight is more or less on time and there is no undue delay for baggage delivery, then I would take the bus.