Sorry for us all being so pessimistic.
I also think that is too early for using a rental car.
We had a very smooth disembarkation and were at MCO at 9:20 using a limo (Southern Elegance - and it was great). When you add in security time and the short wait for the tram at the airport (depending on which airline / gate), I think you might be too late.
So if you add in rental car waiting, I don't think there is a chance.