I take this to mean that you are building an actual tiny house on the ground or do you mean rebuild the RV?
It doesn't seem that the rv appliances would work well, RV windows are usually junk, the cabinets are not like residential and are built in place.
You can buy a much better fridge for $300 to $400. The RV furnace and water heater are for thin thru the wall designs and somewhat noisy. The furnace ducting wouldn't be the same. You can buy a propane or elec 10 gallon residential water heater for $325 and a 500 watt 240 v baseboard electric unit is $35. If you had a small wood burner or fireplace it would use very little wood to heat the place. We are talking more like sticks compared to logs.
If a person wants to cut energy use, taxes, maintenance and initial cost to the bare minimum I think a TH is an excellent idea. I can see the tiny house as a very good way for a person to be far more comfortable than an RV but I dont really see much of an RV being any good for a tiny house.
Good luck to you in whatever you build.