No base model gas V6 in half ton or mid-size truck is getting 25mpg unloaded highway in the real world, and certainly no V8 either. And base V6s are not offered in trim levels with heated leather seats. The only pickup coming close to your fuel economy expectations is the 2014 Ram diesel. Similar V6 diesels in SUVs are getting about 15mpg towing more traditional travel trailers and 25-30mpg unloaded. The Ram diesel is so new I'm not sure if anyone has purchased it yet. The Jeep Grand Cherokee was getting the same engine and was delayed until spring.
If you are willing to get an SUV, there are a few from VW/Audi as well as MB and BMW that should meet your towing needs, FE expectations, and offer the interior seating space you want.