In the fluff skink chiefs tell Saurus what to do. The rules as written do not allow a skink to lead a Saurus. What if Saurus had Ld 7 (and were slightly cheaper) and Skink Chiefs had Ld8? Then a small or very character light army could have Saurus benefit from a nearby Skink chief giving them direction. I guess it covers what you think leadership represents. Is it primarily bravery? I can see a Saurus being braver than a skink chief. Is it primarily discipline, I don't see Saurus as being that disciplined without guidance. What if to represent the less discipline but greater bravery you made all Saurus stubborn? I do however find it generally inappropriate fluff wise and crunch wise for a skink chief to join a Saurus unit directly.
If you really want a skink chief as the general just make your saurus hero a BSB thus making them ineligible to be the general.
That's not what I mean I guess I should say, for the (eventual) new book do you think changing the Ld like is a good idea or bad idea?
Well the way I look at leadership is not just intelligence (which the skinks will have more of than a Saurus) but also the physical command presence that a big bruiser would have. Obviously this applies to the more brutish races more so than say elves. So fluff-wise, it makes sense for a saurus to have higher leadership, not due to intelligence necessarily but being able to physically inspire his soldiers on the battle field. This is held up in the BRB too in some of the flavor text (ie rallying units).