Will it have room enough to carry an 85x instead of the Origin-branded rover?

Until the ship is fully built and implemented this is difficult to say with complete certainty, but the 85x has a much larger footprint than a Rover so we consider this unlikely to fit. While ships smaller than the Rover may technically "fit," the lift is designed purely for a ground vehicle, so maneuvering a ship in there might prove risky in terms of causing damage to both vessels.