The general consensus that I have read is that;
If you can find someone through a user group that is specifically looking for a toad, AND has already installed the matching equipment in their MH, you may get some premium for your unit.
If you are selling the MH, you may get a reasonable amount added to the MH price since the Towed is already set up for that MH
If you have to sell on local market to a non MH buyer, the add ons to use as a towed will likely be seen as a negative to the vehicles value since it likely has thousands of miles on the chassis and wheels that are not showing on the odometer.