but that's not how people think. if you put yourself in the shoes of a big construction company owner, one who buys fleets of vehicles/yr, or every so often...you're not looking at lifetime cycle (unfortunately). you're thinking price, serviceability, and likely have local gas partnerships in place.
your approach isn't wrong, the problem is, that's not how these company owners look at the problem. they just see 4 things
need vehicle
buy good vehicle for cheap price
ensure it's easily serviceable
ok next problem, go!
therefore, building a full-size truck isn't worthwhile, because the customers that truly support these vehicle product runs, aren't there. recreation mid-size truck is a push too, but who knows til it hits the market.