When you rent a reservation from a
DVC owner, your agreement is with them, not Disney. Therefore, all aspects go through them and that would include contact if a room was taken out of service. But, if a room that the owner reserved for you is not available for some reason, then DVC would be working with that owner to make the adjustments necessary for that to happen, so you would not be out a place to stay.
One of the main benefits of renting is obviously the savings. The main drawback, IMO, is that you are not dealing with Disney but a person and the lack of flexibility to make changes--many have no cancellation or change policies--or be involved in decisions regarding the reservation.
In this case, it sounds like Disney is working with DVC owners, if possible, to accommodate them and their guests/renters best they can given the construction that will be going on. But ultimately, any issues with a resort and changes to reservations would go through and need the approval of the owner you have rented from. If a broker is involved, then yes, you would start with them as they would be the ones to have contact with the owner directly.