Wat about using an ULM, such as a Dynamic WT9 as a towplane? They use them in Europe more and more instead of the classics Piper Pawnee, Aviat Husky, Piper Cup, or Robin DR400 etc.

Advantages of those type of airplanes are the good power/weight ratio, decent fuel economy and relatively low operating costs.

Jock - that is entirely too sensible. In the USA we are limited by our FAA to using tugs that carry Standard or Restricted Use airworthiness certification. Under Restricted A/W we can specify glider-towing, and achieve approval for that function. Even though FAA has determined under a different part ( pilot certification) that towing is NOT carrying passengers, they haven't aligned the A/W side of the house to realize that the tug and the glider are separately responsible for their own safety of airframes. So we are limited to mostly Standard A/W machinery for towing.

And the 182 is a great towplane, for all the reasons given above. I ran one for nearly 20 years, and towed a Nationals with Pawnees and a Brave and stayed fully even in the rotation, at density alts of ~8500msl. Pull out the rear seat to eliminate folks asking for ride-alongs, and get better climb rates.