Isn't it better for his development to play 80 minutes as a half (even if it's in NSW Cup) then 20-30 minutes as a Hooker or Half?
We know Mahoney is coming in 23 and he can play big minutes, so his minutes become further restricted there.
I agree with your sentiment regarding JMK, the solution, if Mahoney doesn't come early could be:
9. Cook
14. JMK
That way, we're developing and playing an actual 9, which leaves us in a better situation long term. JMK, for all his shortcomings is pretty versatile and allows us cover more positions in case of injuries.