and if your team also doesn't mind getting manabolted by spirits of men flying 20 meters up, being subject to watcher attacks, being unable to pass through wards, or any of the many, *many* other problems that come attached to being dual natured...
frankly, i think a better use is to have the guidance spirit force the enemies into the astral, so you can drop crazy AOE spells on the poor fools from the astral. and also so that you can laugh at them for having a penalty to their dicepool as an added "benefit" to this supposedly good thing.
(incidentally, you could also use this to trash objects with mana spells, by my reading, and to make astral barriers effective against physical intruders... all sorts of uses, many or perhaps even most of which are best to use on people who are *not* your teammates

)