Repeated personal experience has taught me that sandbox games work much better on forums than games that focus primarily on plot. To that end, I've got a Vampire: the Masquerade sandbox game idea in mind.
I don't have the entire concept in mind yet (I only came up with it an hour or so ago) but the basic idea revolves around a Camarilla fictional city that has recently recovered from a Sabbat attack. With the last stragglers of the Sabbat on the ropes, the Camarilla need to rebuild their numbers to become a flourishing city once again, leaving the Prince to be much more accepting of creating new Kindred.
People who are new to the game will be encouraged to start the game with a PC Sire, but not required. As things get going, recruitment will come in the form of particular players trying to find PCs to play their childer.
I intend to have two different tiers of players. Standard characters will be made using standard rules, but characters in positions of power will be given bonuses in exchange for some compliance with the status quo. For example, if I give someone beefed-up stats and let them be Sheriff, I expect them not to try to stake the Prince. This will allow people to play characters which would normally only be NPCs, filling out the game and taking a lot of the load off of the moderators. Naturally, standard characters are free to plot to their hearts' contents, but will (as usual for VtM) be at the disadvantage of being much younger and less powerful.
Although hunting down the last stragglers of the Sabbat will provide some degree of combat, the majority of this game will be sandbox and political, building alliances and the like. As is normal, outright slaying of an enemy in Elysium will be punished, but getting the Harpies to so humiliate an enemy that they commit suicide is perfectly fine.
This being Elliquiy, spending blood to make yourself appear more human (breathing, warming the body, being capable of sexual intercourse, etc.) will only cost one blood point, and the Blush of Health merit will explicitly allow sexual intercourse as well.
All are welcome regardless of sex, gender, or sexual preference, and you aren't required to play your own biological sex. If you want to play someone who got captured by the Sabbat and fleshcrafted into the opposite sex by a Tzimisce before being rescued, by all means.
That said, I'm only allowing Camarilla, though that includes Lasombra Antitribu and members of the Assamite, Followers of Set, Giovanni and Ravnos who have pledged themselves to the Camarilla.
I'll be using the Vampire: the Masquerade 20th Anniversary rulebook.
If there are questions, concerns, things I've forgotten, or whatever, feel free to ask.