This is most of the current rules.

I think it should be able to have "Fan-based things" in it, for example, Cirno being known as 9, but not any yuri stuff such as Alice Marisa pairings, can be a joke like in some videos also as long as its like this and won't mess up the story line.
The people who are main characters, such as Reimu, and Marisa, could be manipulated, or controlled by the players, but (Haven't decided yet) not the other players.

~~Edit~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`
Also in addition to the not being able to control other peoples characters, until there is a problem, just pm the people who own the characters and ask them what would be able to be done and not... not very good at explaining...