I think it's bad enough that you can multiclass Companions without restrictions in the first place. It shouldn't be possible. Class is about who that character actually is. Gale might work as a sorcerer or a wizard but he won't work as anything but an arcane spellcaster. For Druids or clerics their class isn't an occupation it's a calling. You shouldn't be able to change that without a significant story event.
This is not about any reasonable interpretation of player freedom in an RPG. The only character who is who you want is your character. Anyone else is not for you to shape. Not in class, not in race, not in anything. Except through story events, and those, too, are controlled by the GM and not by you.
So, here's a firm "No" to the question. And I would go further and disallow multiclassing companions at all. I won't get that and I can live with it, but it's my firm position on the matter nonetheless. I you don't want those restrictions, you could make your whole party from custom characters. But you shouldn't be able to destroy the pre-made companions.
Edit: Somewhere above POE2 was mentioned, where you could choose between three differnt class combinations for a companion when they joined. That was indeed an acceptable compromise. Companions could be different but you couldn't spec them in ways incompatible with their story or presented identity.
Yet another example of somebody wanting everyone else to have to play the game they way they want it played.
If you don't want to multiclass, then don't. If you don't want to respec origin characters then don't.
The parts relating to story events are just nonsense. All the characters in the game had a life before the game begins - so what? I've played with Gale as a cleric and Shadders as a paladin - it worked for me.
