They could set something up so creators could mark videos as premium, and then people have to pay a certain amount to watch.

Google already has the payments side of things covered from their other services, it really wouldn't be a stretch to add something like this.

Creators are basically having to do this anyway using a different site (Patreon) so Google should look at how to bring that internal to them.

That also neatly sidesteps the whole demonitized for being advertiser unfriendly issue, because the only people paying for various content are people who want to watch and support such content.