Honestly, I don't see the need for a Lizardment lore. I think that fluff-wise it doesn't fit (as the standard lores were taught to the Lizardmen by the Old Ones). As for fitting the army like a glove, both the Lore of Light and Life fit like a glove. What do saurus lack the most? Initiative and weapon skill. What does Light give? And the Lore of Life just rocks, resist miscasts, regrow expensive units, make things tougher and harder to kill, and passively heal monsters.
Our own lore would be nice however, i just think that we should be allowed to use 2 Lores provided they are both Life and Light at the extra cost of 20 points. Could also work in a rule that the slann needs to take Mystery. I think also Skink Priests should have the choice of Life, Light or Heavens.
I think Beasts, Light or Heavens fits skinks better fluff wise, we also need skink high priests and Warchiefs (lords).