Here's another thought.
Just say you have a raid in a Dwemer ruin. You have a group of 9. (All as examples)
You are doing the raid as normal. Killing bad guys, opening doors. Then you reach a large junction with 3 exits and a control panel. The panel requires your group to split up. (You see where I'm going with this?)
Your group needs to split into smaller groups in order to activate the panel at the junction. The group must decide who will go with who.
This could set up for some interesting interactions. Perhaps if one of the smaller groups fails, they will need the other 2 to come save them?
Just some more thoughts to think over.