I wonder?

If everyone was made to pay for their account, or all free accounts were only allowed to go to level 5, what the population on the server would be then?

I'm gonna go with …. "lower".

Just like any other f2p game.

This game could become more than a game if it had affiliate marketing tied to it. Suppose you had a link and advertised or posted simple posts about the game with your link and people became Noble citizens and you earn $1 for each month a referral paid their subscription… That way advertising costs are low for rat labs and you are incentivised to keep your Noble status otherwise you don't qualify for either pay or credits. I'm a professional online marketer and this is how it could grow the game and have a loyal base of paid accounts. I could set this up for rat labs if they need a pro.

you earn $1 for each month a referral paid their subscription…

This is a legit question because I don't really know anything about the referral market world and am genuinely curious. You say $1 and although that doesn't "sound like much" it is actually a full 20% of that revenue. Is this in-line with the industry? Or is it usually something other than 20%?