Well you have answered my question with your first question - what was Sammy's contribution ?
I think with all his experience he was much much more than the bib and cone man, he has managed, albeit poorly, and coached at the top level, he was on the England staff at one point (under Sven?) and I cannot see that his knowledge and experience were wasted for two years.
My point is that SKD will have nowhere near the qualities that Lee has. A good addition to the staff - of course, but as a replacement like for like, no way.