My suggestion would be so easy to implament. Making some of the skills/abilities further up cost more than just one point. You would then be forced in some situations to think if it would be better for you to wait untill the next level to get the advantage.
I hope you like my idea and you have my full permission to use it without having to give me royalties and such. 
(or you can choose to hire me, I'm cool ether way)
Charles
