If you are still accepting, I wanna throw my hat in! In case you are accepting, here are some questions (ignore if you aren't accepting anymore).
We have to be human, is that right?
Would the characters meet in the beginning of the RP or already know each other for a short while?
Do they have to be some sort of scientist? What kind of jobs are acceptable for them to have? Will they leave their normal lives (former jobs, family, friends) behind for their search for the truth?
Is their 'search' (as I call it now) a job, aka do they get paid, or is it a hobby?
Do they have 'special rights' that normal civilians don't have? (talking X Files - they're 'cops', they get into places, interrogate and have access to files and to medial supplies and the like. Do our characters have any of the like?)
Is the story completely driven by the characters (the players) or is it GM / co-GM driven, so that things maybe happen 'unexpectedly'? Do you know what I mean?
Okay those turned out to be more questions than expected, I will stop here.