I rented an exchange vacation from a DVC rental agency. They told me upfront what kind of rental it was and the extra fee involved. They gave us a guest certificate and the owner of the exchange put our names on the reservation. Absolutely zero issues. The cast members were very aware of how to deal with a guest certificate.
Yep, 99% of the time it will go fine. Cast members don't tend to be aware that there is a contract violation in play. However, member accounting is aware, and management is aware. Its likely to be fine because its unlikely that anyone who cares will find it. Of course cast members know how to deal with guest certificates, that's a perfectly legitimate way to exchange into DVC - what isn't legitimate is then selling the reservation.