if i understand what you mean skynet, yes because sp and mp are combined as side a bunch of times in the vids and forums, but you cannot use them all at once
No you didn't understand at all.
Here my attempt at simplifying it. You can make 16 characters and choose from those 16, you pick one and enter single player, the other 15 characters you did pick are then used by the AI as you allies and opponents in the campaign. So when your running around you see the characters you created fighting with you and against you.