This is a tricky issue.
We had a similar time in the past when a great half back retired and we couldn't replace them - 1989 was an example when Turvey retired, Hagan left and an unknown from outside the club replaced them (Greg Mackey). We had no local product ready to step into the role. Mackey didn't work out. That set us back as a premiership force for a couple of years - even with Terry Lamb in the side - until Polla-Mounter hit the scene.
In 2004 when Thurston left we had Sherwin in career best form so it wasn't the same set of circumstances.
After Noddy retires, we are like 1989 again IMO. Old half retires - no obvious local coming through the ranks fast enough and an unknown in Blake Green joining the club. No offense to Green - he had great pedigree as a junior and could be the solution. Also, we had Lamb in the halves back then - and Roberts is Ok but doesn't give us an alternative organizer.
So I think we are trouble in 2011 in an organizational sense. That was our problem before Noddy and Roberts will NEVER fill that role.
Thurston seems to offer an instant solution to bridge the gap at the right price. On that basis, I think he is the best solution for team performance (I can't comment on all the moral issues being raised).
But TBH I think he is just pumping up his price in the market and we will never chase a salary cap gorilla like SBW again - so we better hope that we get somebody like Mortimer into the club.