Only H/W heaters I've seen with an adjustable thermostat are the ones you have to manually light the pilot.... The convenience of flipping a switch in the trailer outweighs the ability to control temp in my book. If the wind blows out the pilot, your out of hot water, the DSI will light itself.
2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.
Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.