[quote=@Saffirra Dusk]
You know.... Why don't you just add the others??? Does it have to be only 5E?? Can't you combine them? Or are you incapable of doing so?
[/quote]

The system is different as it is a revision from the previous edition. Simply putting a mix of them will not work as the class' mechanics are different in each edition.

In an analogy, they're different realities in parallel universes.