Progression assumes expanding your character into having followers, servants, slaves, minions etc. Not too many games have formal rules for taking territory and mass warfare and generalship. You can tax your followers or if you're a cleric you can power up by gaining worshippers for your god.

Ah that's awesome, I'm actually doing something similar for my (PC) co-op RPG in terms of gaining power over time, rather than just straight "superhero" damage/magic power.