Our 2007 Komfort Kampsite is decently insulated on the sides but that doesn't mean a whole lot in regards to the OP's identified TT. Ours does not have heated pipes or holding tanks but that doesn't seem too hard to add. Our is a 26' coach (point to bumper is 30.5 feet) and has a GVWR of 9500 lbs. Construction on it is not a lightweight build. Ours does not have double pane windows. It is more of a 3 season TT. But again, not the same model line as listed in the OP.
Per the recommendations on Nash/Arctic Fox, Bigfoot... yes those are great 4 season trailers but also generally end up being very heavy for the size. His 4 Runner would be questionable as a TV and it does not sound like he wants to upgrade TV.
Check all the seals on the top of the TT to see if it was well maintained. There should not be any signs of "caulking" (actually Dicor) that looks to be cracking or pulling away. Severely cracking Dicor has the potential for a water leak.
