Privateers & Prospectors
While working on a new campaign setting and dungeon last night I was thinking about the role that adventurers could play in the game world.
Instead of being MurderHobos wandering the countryside plundering whatever bit of gold isn't nailed down PCs are Privateers and have Letters of Marque from the King giving them permission to tomb raid, skirmish with enemies of the kingdom and otherwise act like hoodlums. Training costs represent the percentage of recovered treasure owed to the crown. Gaining levels is tied to increased social standing in the kingdom as the players acquire wealth and reputation.
PCs would organize expeditions, hire retainers, and even gain patrons and sponsorship in a manner very similar to how Privateers operated from the 16th to 19th century.
There's even the option for some parties to have their Letters of Marque revoked for various reasons turning them into outlaws or bandits (much like pirates).