Player input: learning from the past
I'm a Hero System player from way back. And a GURPS player as well. That school of RPG design had a prominent feature in it's use of character disadvantages. Mechanically speaking, the idea is to trade some options for how you play your character in for more points with which you can buy abilities. The intention is to encourage you, the player, to develop your character beyond the simple archetypes of whatever genre you were playing.

It's an interesting design choice. When coupled with detailed and number-intensive character creation systems such as Hero and GURPS it both encourages players to think about their characters in relation to the setting and the stories they want to tell and it encourages very careful balancing of cost versus gain when creating characters. In myself, and those I know who played those games, the system tended to produce a strange hybrid of story-conscious dramatist and min-maxing powergamer.

At heart, however, the idea of disadvantages is a positive step toward the type of player input that I have been talking about and that I aspire to. Think of this: you are making your character, Spider Man, in Champions. You take a disadvantage that says you have an elderly aunt who gets into trouble. The level at which you take that disadvantage tells the GM how often you want the story to involve your character's relationship with his aunt, and how useful you want her to be to him in general. You are very clearly creating an understanding between yourself and the GM on the metagame level.

It rarely worked that way in practice, though. My long experience showed that most players ended up using disadvantages as ways to get points and often hoped and prayed that the enemies that they chose for their characters never showed up to ruin the adventure. Likewise, most GMs seemed to pull out disadvantages far less than they ought by the rules--favoring instead to focus on the plot that they had come up with beforehand. That's not to say that people didn't use character disadvantages as tools with which to define play, but the combination of the mechanics with cost benefits hampered their usefulness as such.

A slightly better tool for getting the player's desires into the game came with 7th Sea many years later (perhaps earlier, but not in a game I've played). The concept of backgrounds in that game gives the player the option of investing in aspects of the character's past and then getting a reward when the background comes into play. So you pay for your messed-up backstory at character creation, but then reap rewards when it comes back to haunt the character during play. The brilliance of this is that players have invested, so thay have incentive to prod the GM into bringing their stuff into the game.

Even more interesting is the idea of Spiritual Attributes introduced in The Riddle of Steel. I haven't played this one yet, so I can't comment directly, but the idea is that things the player decides are important to his character have mechanical weight.

I'm still struggling with what I think is the best way to arrange the understanding between players about what is important and how to proceed with that knowledge into storytelling. But I do think analysis of some older ideas is well worth the time.