With what you're describing Aiken, you could probably manage this sort of party split while using Dynamic Lighting (currently only available for Supporter and Mentor accounts). If the players can only see their own light source/field of view, then the player who has split off in a different location on the map can only see what they see and the rest of the party can only see what they see. So this sort of split is doable if everyone's on the same map.
As for splitting the party up so some of the players can be on one map and the rest of the party is on another map isn't currently doable. You could probably try running your game with two clones of the same campaign and have one half of your party logged into one campaign and the other half of your party logged into the duplicate. Though that would be pretty messy if you use the built-in video/voice chat.
