Isn't this sort of a subtrope of Sibling Triangle?

Does anybody agree that we should create a separate trope for when a twin or look-alike literally replaces their other half for good because they need to fulfill the duties the other couldn't or something similar like that?

I just think it's a pretty drastic difference between two twins switching up for mundane reasons (like say on some disney channel show or comedy) to actually replacing another for the sake of filling that persons shoes. (Done sometimes in anime,manga, and soap operas.)

For example the twin death example in Naruto or Angel beats where one has to live on a certain way BECAUSE of the other's death. It's not so much a 'switch' as it is complete replacement. A switch implies the 2 pretend to be each other, which cannot be fulfilled here. Another (non-death) example I can think of is in 'Witch Hunter' where one of the brothers takes the other's place so he can escape inheriting his dynasty.

Point is, I think we need another trope (sister/daughter?) to separate the issues.