Eldunari from Eragon, much?

@Ihhh  
True, I just don’t see it happening for the show either. If the concept were to be implemented anywhere, I would imagine it would be in the comics first and foremost, which is also where I would most like to see this concept implemented. Although, I don’t really see that happening either. But if it were to be, I think it would be interesting.  
But of course, I could be wrong about my expectations.
 
If nothing else, I guess it could always be explored by fanfic writers.

@Howaito  
Keep in mind that the idea was only rejected for the movie. There’s no reason the show or a comic couldn’t use it.

Assuming this were a canon they would go for, it could make the Crystal Empire and its crystal heart pretty darn interesting. Also considering how much of a role Spike played in handling the crystal heart.
 
Spike grew up among ponies who supposedly know only very little about dragons. Could you imagine if some dragon, e.g. Ember, would know about dragons having crystal hearts, and one day while visiting Spike in the crystal empire, she would come upon the kingdom’s crystal heart? Imagine what that could lead to.

Holy shit!

Then Zant appears.