[Ranylyn]

I don't see why not, but are there actually any two promotions from the same base class that have benefits to main class? I mean, I completely see why some would prefer to level Kensei faster, but it also has no main class only benefits (outside of the base class, which is locked in for Destiny,) unlike Ghost.

This suggestion would basically let you focus on levelling the other class up faster despite the promos, and also serve to future-proof future potential destinies against being dicked over by new classes/ skills/ balance changes. So I definitely don't see why not. Like Sderg said, being Destinied already gives up a lot. But it's not an immediate priority.