I was wondering is it possible to play with the Guild Subhouse in campaign mode? When I played through the game the first time I never allied with the Guild. Now that I picked it up again after a while I tried choosing missions so that I would end up allied with the guild but I couldn't. All the missions seem to circle around fremen sardukar Ix and teilaxu.
I would say it's whoever the army is loyal to. This almost automatically rules out the mentat :- I mean if the army follows the commanders who have deceided to take the throne by force, the leader is pretty much powerless.