Oh I just thought of an idea (actually it's from FFXI). They might make it like, for example:
You are a lvl40 *insert class here* - you can only grab and equip skills lvl20 and below (from any class)

Kinda like from FFXI with mainjob/subjob system right?

Err....Oh well, I'm just too excited to know what really is going on. D: