I was hoping the StoryTeller adventure truck would have been about the size of the 27North Rexrover, but seems like everyone wants to jump into building the ER sized vehicles.
I agree with your sentiment, most rigs seems to be growing, especially in terms of weight, but unless I'm missing something, the Rexrover, GXV Turtle&Adventure Truck, Earthroamer XVLT/LTi, ST Hilt, etc. are all roughly similar in size and represent the available "mid-size" of what is available in the US when it comes to a US-built chassis trucks more or less permanently bolted to a camper body. The Rexrover might be a couple feet shorter? Tough to tell and maybe I missed the detailed specs on their website though I will mention the website says their truck is under 9k lbs and if so, very impressive: a base F250 weighs 5500-7500lbs. I think if a buyer wants a reasonably capable 4x4 camper with interior shower, toilet, cookstove & sink kitchen, full-time bed for two adults and additional smaller bunk/bench conversion bed(s), along with some gear storage and decent fuel&fresh water carrying, it would be tough to do in a significantly smaller package than what is currently available. Weight is probably the main area to improve, particularly with so many of the aforementioned features being considered popular market demands vs commonly eschewed options. Throwing out a hasty dreamsheet, I'd personally aim for the following baseline: high and low-range 4x4, locking front and rear diffs, 12" ground clearance, 800mi range, cruises hwy @65-75mph, simple+reliable motor that is somewhat DIY maintenance & mod friendly, 50gal freshwater w/onboard filter/purification that can pull from any freshwater source, sleeps 4, good heaters, hot shower, simple toilet, range&oven, seatbelt seating for 4, dining/relax seats for 4, plumbing&electrical systems that reliably function well below freezing with no shore power, siped and/or studded tire available for winter, gear lift on the back that'll hold two spare wheels + a dirtbike or 4 bicycles/skis, etc.....all in a package that is well under front and rear GAWR unless the vehicle was originally designed by the engineers for a ton of off pavement 4x4 driving. Perhaps this is unobtanium in this class of vehicle. A lot of folks want the turnkey but IMHO, a fun part of the challenge is realizing that your rig has some of what you need but there are always a few things to work towards. Maybe the real adventure is getting out there having a good time with what you've got.