Buses have been used for many purposes after they have been retired. I have never been in the towing business. Although I am fairly sure that you could haul a car or truck on a bus frame, I don't think that the bus would be maneuverable enough to act as a tow truck.
Also, it would take a whole lot of work to get a bus to this stage.
I am sure that you will get a bunch of responses and ideas from the skoolie family here.
I am not trying to discourage you. If you have a dream, then make it so.
It sure does look cool, though.