Binding a spiritual dream traveler as a familiar

Inspired by the discussion about other unusual familiar binding options, I stumbled upon this.

A spiritual dream traveler is a spirit in the dream, with a might score equal to the imaginem score of the magus. It seems then reasonable that a physical dream traveler with the "spirit familiar" virtue could bind him as a familiar spirit; and if the vis used was real vis brought into dream, the binding would persist even when the spiritual dream traveler returns to his body in the real world.

Hmm. But how would the spirit (of the spiritual dream traveler) now reunited with his body interact with the familiar bond, in particular in terms of spending its might points?

Who says the spirit has to return to the body? In my "reading" of canon, the spirit is a momentary snapshot of the immortal soul, which can not be affected by magic. Spirits can, of course, be affected by magic, which is why your idea would work. I would just say that the "dreamer" who's spirit you are binding, doesn't get knowledge of that dream.