Well, the last two things you mentioned are part of the QB system, and that is a totally different component than MP.
To make it more clear, BC utilizes a system (not your "regions") of campaigns, each campaign as atleast one episode and each episode has atleast one mission.
QB is a campaign with one episode and one mission, and the mission, practically speaking, never ends.
MP is sort of a specialization of this system with additional constraints to prevent cheating.
To do what you want to do you would have to write a new MP mission. This is possible, KM did this as well.