I think this really needs to be done.

Nobody in this game's community would kick someone from their level-synced group who doesn't have all of their skills yet. The playerbase just isn't like this. It doesn't hurt at all to allow us to use all of our skills. In fact I rarely run level synced content anymore because I hate losing my skills.
Heck it might make new players become even more excited when they see the skills they'll be getting later on.

It's just silly. It's overthought. It needs to happen.