Alright, I think we've got enough players to to be starting off with.
The LoS's HQ will be in London (Brittania), I think that's appropriate. The Club...I thought of France, but I think it needs to be a touch more exotic to reflect their slightly more exotic origins. Maybe one of the French colonies in Africa, although that puts them a continent in between their rivals and any possible action in the Republic of America. I know it's fictional, but logic would accord the Club being at a disadvantage geography wise. Any other ideas for Europe? I don't imagine they'd be nestled in America, but if someone gives me an apt argument...
First plot will be a race to cavorite! The gravity-defying element, the superior alternative to steam-powered airships, and the option to give either team (or the Mystus Order) the power to build very swift, clean and powerful airships, to either use as high-speed travel to any place, or as an intimidating weapon used to assure supremacy or challenge the dominant powers. A starting plot not too complex in itself, and allows for action whilst
If either PC team manages to get it, they both have access to government workshops that can work the cavorite into existing airships/zeppelins/whatever air travel vessel you want. LoS will be able to pull strings with one or a couple of governments they have done favours for before, and the Enigma Club's shady benefactors have their own contacts.
I'll let you come up with what you think each team's headquarter's should actually be (a museum, a disused train station, a pub, an old ballroom...) let me know if/when you come to a decision in your respective teams, and I'll get the starting IC threads up.