I’ve had an idea that I stumbled into. And that is the idea of giving your players a character or class goal to work towards during the session and if the complete that goal then they “level up.”
I had the thought that this might also be a tool that could lead the characters to details and clues about their quest that they might not find otherwise.
At the beginning of the session, each hero is given a personal goal to achieve throughout the adventure.
If they achieve their goal by the end of the adventure then they get a milestone towards their character build.
Example
Your earn a milestone in progression if you achieve:
Shadow - sneak attack 5 different monsters
Guardian - take more damage than any other character
Mage - be cautious and search for magical stuff
Archer - keep cover during the battle and while attacking
Priest - say a prayer and bless the party at the beginning of each battle.
Wildling - find a way to defeat an enemy using your environment
Commander - empower your party with a battle cry during combat
Blade - be the first to strike your enemies