Simulated Open World VS True Open World VS Linearity?

[Koh]

I personally don't like it when enemies scale in relation to the player characters' levels because it turns grinding and leveling up into a moot point.

This is what I was thinking about that being a constant thing too. Which is why it has to happen only once at some point, to set the average level for future areas. I'm sort of leaning towards Goemar's initial suggestion, where after X number of areas, the average level increases or something. But I'm all ears for any other ideas.