Why not make an MMO in which you can create 2 types of characters:
1. Normal "adventurer" characters, and
2. Hero characters.
The difference is, the hero characters get some pretty cool unique abilities, and they make a significant impact on the world. As in, you get written into the lore, and are recognized by NPCs more widely. You have a few more options, such as political sway, and get to engage in some of the more epic parts of the game. The catch - Heros get perma-death. If they die, that's the end. They might build a statue of said hero, but you don't get to play them anymore. You can create another hero, but the one that died is now integrated into the world.
Good idea, bad idea? Haven't really thought it through yet.