Consider adding a capstone like enhancement for racial enhancement trees. The "AP spent in tree" requirement would have to be much lower than PrE tree capstones for anyone to take it. Even then, it would be passed over by most builds for more prestige enhancements. As a result, the only way to make them tempting would be to make the very powerful, yet not game breaking. Personally, I want this badly for my halflings. I know there is a huge elf following that would most likely want something similar.
+2 Hide, Jump and Move Silently
+2 Attack and Damage with thrown weapons
+2d6 Sneak Attack damage
Normally, this would be too much for one enhancement, but most players will pass it over for more appealing class enhancements, especially considering the "AP spent in tree" requirement and that some builds don't use any racial enhancements.