Cassandra, I think Georgiatickler's advice was not bad: in a poll you have a very simple voting system, having the results immediatly available and already displayed in percentage, but still the posters can post their ideas and suggestions.
Plus, maybe there you could attract attention from a wider number of forum members (people love to vote :->).
As for the scenario of the roleplaying, everything you suggest is fine, for example the medieval is ok, maybe more a fantasy-like environment, like those in D&D, not really located in a specific place and time. This would be the most simple scenario to build, since a medieval setup has well known feature everyone recognizes.
A future scenario would probably be too "free" and there could be divergences in what kind of setup to use: space opera like Star Wars, or based on a specific "fan world", like Star Trek, and so on.
Based on a video game: too specific in my opinion. There are a lot of people here who don't like them, or don't play with them or simply are a bit out of age target, like me: I used to play a lot with video games, when I was youger, but now I doubt I know any of the games younger people here speak about. If you can't recognize the references, it gets boring fast.
Modern scenarios are good, but they should be based on situations/environments where you potentially have a lot of different people who can interact fast and without excessive "social inhibiting" factors. An example: a college dormitory.
I love the idea of having a scenario in which women dominate men, with a subsequent change of the roles, or the other way around too. Any way it should be a game in which whoever takes part could find his/her own: so, if you are, say, a male and strictly a tickler, if the story is temporary in the "women dominating men" phase, you won't have interest in joining. Probably we should consider the possibility of having more than one "paths" of narration in the story, even if in the same thread, so people who have more defined tastes could find their own too.