What issues would you have with letting a player level into the same class, but a different subclass?

What issues would you have with letting a player level into the same class, but a different subclass? It doesn’t appear to be RAW.

For example, I am kind of “finished” with what I want from the archfey warlock subclass. What would be different about choosing a new subclass instead of just a whole new class?

mikemearls15 points21 days ago
we don’t balance for that, so expect some amount of brokenness.Comment