I'm not seeing what the big fuss is about. FWIW, the new UP "flat wheel" sound boxcar I just picked up has diecast trucks, hidden uncouplers that are removable, and the Kadee mounting blocks. The couplers seem to work well, they couple very easily, and don't come open, at least in a 20 minute test run with a pair of track cleaning cars behind them to provide a drawbar load. At least this truck design, to my way of thinking, isn't really all that bad.
I think the buzz about spring loading of the trucks on rolling stock is a lot of ado about nothing. The springs don't do a think unless you put about three pounds of lead in the cars, they're just cosmetic. As far as the fixed coupler, that hasn't been an issue with the vast majority of rolling stock I own that has fixed couplers, exactly what is the big deal with those?