Quote Originally Posted by knife eater View Post
The manga defined a Bloodline Limit as the ability to combine two elements to make a completely new element (Water + Earth = Wood). You have to be born with it (or genetically modified). That's why you can get two people who are born into the same clan, but only one inherits the Bloodline Limit of the clan (Take Hashirama and Tsunade as an example). It isn't something that can be taught or learned. If it could, Kakashi would be using the Wood Element just like Yamato. Kakashi can use Water and Earth elements just like Yamato, but only Yamato can combine them both to make the Wood Element.

In my opinion, you're just making it more difficult than it really is. If you are born with the Bloodline Limit, cool beans. If not, you just don't have it. The only exception to the rule seems to be with Eye Bloodline Limits (Sharingan/Byakugan) where everyone seems to have it in their clans.