Practically there are no zero visibility landings. There is reduced visibility of varying levels. Reduced visibility landings are only allowed when the appropriate ILS equipment is operational.
The practical issues are actually not the landing itself but separation from aircraft landing afterwards. On the ground the runway lights are bright enough and close enough for slow navigation. However the aircraft takes longer to clear the runway and this means increased separation between landing aircraft is required. It is this that cases delays as aircraft waiting to land are pushed further and further back.
A ground tug to facilitate speedy removal of the aircraft from the runway makes sense in theory but would be hazardous and the acquisition time wold be non trivial. While an estimated stopping location could be calculated for an aircraft finishing its roll out after landing it would be subject to a very large variation and the tug would have a large distance to cover to get to the aircraft. It would then have to connect and start the tow. The question is whether this wold be quicker than the current arrangement and what the mass penalty would be in terms of changes to the aircraft structure to enable it to use the tug.
Edit: In response to comments I would like to clarify that my point about the acquisition time of the aircraft by the tug is concerned with the non trivial and varying distance the tug would need to cover to reach the aircraft. Any tug configured to pull an aircraft weighing in excess of 100tons would need to be large, heavy, and have high torque to help it safely move the aircraft. These are all things which will reduce its top speed and so increase the time it takes to get to the aircraft from some optimal starting location.
Multiple tugs would increase the probability that the aircraft would stop within optimal distance of one of them but would also increase the collision risk and add complexity to the local airflow over the runway.
To facilitate quick response and removal of the aircraft from the runway the tugs would need to be located close to hand. However they cannot be on the runway and would be required to be back from the edge by a significant distance. When you consider the finite number of taxiways and the sheer variation in aircraft roll outs this presents a very wide range in possible locations the tug would need to get to with a consequential increase in response times.
When an aircraft lands it typically uses a small amount of remaining velocity to keep it rolling and move off the runway. This would almost always be quicker than waiting for a tug.
-Hybrid tug system
A hybrid system in which the aircraft uses residual speed to clear the runway and meet a tug has some advantages in terms of optimal tug positioning however it reduces the advantages in fuel consumption and increases the amount of vehicles independently moving around the airfield.