Zeusz

You could use recalls in a way like that.

The system works like this: After each session everyone makes a record of what happened from their character’s point of view. These can be used in two ways:

-During sessions you can recall one of these events (“This is just like that time in Budapest”) and get bonuses to that roll. This can be done once for each record in a session.

-Between sessions you can spend records to improve stats and add assets/powers whatever to your character. Spent records can’t be used during sessions anymore. Each type of improvement has a required number of records to make. (think: improving skills is easier than getting better attributes)

If you as a GM rule, that only records with relevant experience can be spent to improve stats, it can be an incentive to do what you want to improve

Cortex Prime has systems that let you gradually improve the characters bit by bit instead of levels either through spending xp or using a system called session recalls