That'd just piss people off. I can already imagine people screaming that "easy mode" would be locked behind a paywall if he did that.
Instead, I'd just prefer it if the dev released more content for free instead of locking everything behind a subscription. Or at least had a one time payment thing.
Because right now paying monthly in order to access a game is not something I wanna do and I'd gladly drop $10 if it meant I had permanent access to the game.