Been thinking about Burning Wheel a lot recently. And through this I've come across a few different criticisms of Fate which basically say that aspects don't provide enough player drive forward motion, and the GM tends to do most of the heavy lifting of the plot. I've been thinking about campaign play in Aspect Driven Fate - basically, I want aspects that are like beliefs.
To that end, I am thinking about a simple hack to Fate Core. Firstly, give the players the standard array from FAE - High Concept, Trouble, one aspect - in terms of their initial aspects. If they want a greater number of aspects, they can be voted on and off, like a trait vote in Burning Wheel - seems most logical - but not really the important piece.
The important piece I am thinking about is Milestone aspects. These are advancement tools which allow players to set their own goals and drives. Giving players only a few primary aspects originally, but allowing the aspect vote to give them signature equipment or allies is important since it stops aspect creep. After that - set some aspects. Each aspect declares what you need to do in order to get that level of Milestone. A minor milestone aspect might be something simple, like defeat the monster at the end of the dungeon, expected to get done in a single session. A major milestone aspect however might be something like taking over a kingdom, or learning what happened to your parents. These events would meaningfully inform your choices as to where your skill points might go etc.
Many of these milestones should contain some character backstory and flavour, they should definitely be compelable, and sometimes should be invokable for effect against you. They are often going to be usable for you, since it is going to be the drive of the story. Conflicting goals of different tiers will get you a lot more fate points than simply steps toward a single larger goal.
Therefore we could have a character sheet like this:
High Concept: Barbarian Warrior
Trouble: I only see the world through immanent threats and desires
Aspect: The sword Sigwulf which I pulled from the guts of my mentor
Minor Milestone Aspect: Capture the lord of this hamlet, so I may question him
Significant Milestone: Help my friends locate and defeat the local tyrant
Major Milestone: Gain back the memory of killing my mentor, and learn why I slew him