My worry is that without adding the fact that it needs an exotic weapon proficiency (or being elven) to be able to use them, they will quickly replace the rapier and make it obsolete (doing more damage in the case of the thinblade). The Exotic weapon proficiency was (I assume) added to restore ballance to these weapons.
Now that you break it down like that, I completely understand why you suggested not to implement those unless the Exotic Weapon Proficiency feat was tweaked to add them. I guess I just didn't realize how powerful they were until you mentioned it.