If a table allows for a collective Dreaming (or collective Unconsciousness), getting there while conscious should be difficult...and interpreting what you find in a dream to be VERY difficult, and requiring Scholarship and Investigation.
(My image was for a tall, pale, black haired man dressed in shifting garb, quietly inquiring as to what business you might have in His Realm...)
As for allowing someone to 'take charge' for a bit...
Hmmm. That's a VERY grey area, at best. The Council might very well rule that a mundane CAN'T give reasoned consent to such an act, any more than a minor can agree to certain acts, because the mundane simply can't understand what they are asking for, or agreeing to.
Personally, I might allow transformation, simply because it fits many stories and legends, and because free will isn't being affected (if the target consents to or wants such a transformation). There might be a great story hook in it as well; what if the target deceives the wizard and uses their new form to murder some people? Now, the wizard is being accused of being a Lawbreaker, both 1st and Fourth! "I didn't want to do it; some strange compulsion drove me to kill that guy!" The group must try and prove the wizard's innocence, and the 'victim's' guilt, before the Wardens take action...