Is this a reach?
Okobi may not be the same after this surgery (we can only hope the opposite), but does it seem logical to maybe see if Simmons can handle the C spot? An offensive line of Marvel/Faneca/Simmons/Kemoeatu/Starks seems reasonable for next season. From what I recall, Simmons is known as a guy the could possibly convert to C. I also recall that Hartings did the same thing. I think Simmons is a very capable lineman that has battled so hard to keep a spot. It seems like Kemoeatu is a guy that is held with very high regards amongst the coaching staff.
That seems like quite a talented offensive line, especially if Kemoeatu pans out.