I am a fan of games such as Mount&Blade where you typically lead your own forces into battle to ensure maximum success. I feel that simply sending your followers out on missions is too impersonal, not to mention how the hell does it count for game play when you're sorting through menus?
It would be simple to add a number of generic scenarios in which players can personally accompany their followers into these missions rather then always having to sit back. Not every scenario needs its own special story driven by plot-armored NPCs as too many instances have become. Just slap together some maps involving the group taking a mine or some fortification. If a random person with the map editor can cough out a fortress filled with NPCs that is more sophisticated than what has been implemented in-game then it shouldn't be too difficult to provide dozens of random scenarios for players to tackle alongside their followers if desired.
The option to personally participate in each of these missions would be up to the player, but aside from its own reward of experiencing the glory alongside your followers it could also allow for extra random loot drops from your fallen enemies.
Just my thoughts. It would make garrisons a lot more of an interesting feature and possibly expand it beyond what I have seen so far: A hacked down map editor where sorting through menus is acceptable as "game play".