I was reading this post by Nordicus and it got me thinking:
Rather than have a static cap for players using a free trial, wouldn't it make more sense to have the trial level cap linked to what you'd been doing?
I don't have any idea of what would be in your game or what the technology would be, but from the player perspective the aim is to have them actually doing stuff, and stuff which makes life more interesting and fun for paying players.
If you tweak it right then you will have the free players both improving the in-game experience for the paying punters, and building their commitment bias so they will eventually convert to paid people, taking their lovely good attitudes in with them.
Super good or super evil people might even attract mod attention and get given free access.