Do you think the game would die without the PC playerbase?

[Lanadra]

PC playerbase wouldn't quit but a large portion would leave if 3rd party was banned.

X to doubt there. You're severely overestimating how many people use 3rd party things. Even just the fact that it's not allowed will keep the vast majority of people from going there. And make no mistake, it is not allowed, regardless of whether it is actively enforced or not. So no, I do not think a 'large portion' of the PC playerbase would leave over it.