I think a lot of people that have huge 2000 lb. plus horses would be happier with 900- 1300 lb. ponies. Some use half draft and half light horse, but a pony of draft type would weigh about the same as some of these crosses and be thicker built and more compact, thus easier keepers. That means a lot if you make a living with them as I do. I log with them and keep the better logs for lumber and sell the rest as firewood. I sell abut 150-200 cord a year and cut and sell year round.
I’ve tried the D-ring harness but it doesn’t work for me. It’s nice because there’s no weight on the neck, but if a horse runs or even trots the end of the tongue whips violently in every direction. That should be mentioned in some of the articles about them. I know you say a work horse gets his work done at a walk. I don’t own any woods but have to travel quite a distance to get to some of the woods I cut in. It would take a long time to walk all the way. And going up hills I let them go at a full run. It’s much easier to get up the hill.
To dig with a slip scoop the dirt must be fairly loose. If it isn’t they used a hook shaped ripper to loosen it first. Your lines must be around your back under one arm only, not around your waist, because if that scoop trips unexpectedly (and it will) you want to be able to get out of its way. Ideally your lines should be just long enough that when starting out between handles you can stop horses by leaning back and to control speed. You don’t want to be leaning too far forward, it’s like a walking plow, you must be comfortable, it’s hard enough work without making it harder.