Given that he looks older than 3 weeks, so fully unfolded, I like him a lot.
There are 3 main things to look at in all horses, regardless of breed or discipline, in work or not, as long as they’re old enough to be fully unfolded:
1 - pillar of support. Where does a line drawn vertically through the “crease” in the front cannon bone (between bone and tendons) come out on top, relative to the withers, and on the bottom, relative to the back of the foot. The farther in front of the withers, the lighter the front end is, and closer to = more front heavy. This guy’s line comes out well in front of his withers, and that won’t change. What will change a little from now to when he’s more like 3, is where it comes in relation to the back of his foot. This is because as he gains weight, that will drop the pasterns a bit, which puts the foot a bit farther in front of the leg. It’s hard to tell what’s what here, whether the picture is tipped a bit, whether they’re standing on a slope, but either way, this guy’s lower line is at least good enough, and possibly very good
2 - neck emergence - where does the bottom of the neck emerge out of his chest, relative to the point of the shoulder At or below, and it adds weight to the front end, the neck isn’t as functional in terms of balance, ability to lighten the front end, using it for power, etc. Above, to a degree, makes the neck more functional. Emerge too far above and it takes away space for muscling. This guy’s looks good enough, it’s a bit hard to tell.
3 - LS gap. Lumbosacral gap, where the the lumbar spinal processes (which angle forward a bit) change to the sacral bones which angle back a bit. There’s a physical gap there. The ideal is to sit directly above the point of the hip because that gives the best balance and power, and ability to flex which is required for push and power. It’s hard to tell from this picture. His may be a bit behind, but a bit either side is still fine.
Those 3 things determine how functionally uphill a horse is. This guy looks pretty nice in that regard
Regarding the camped out look - at this age, he NEEDS to look like that. His leg bones are nearly their adult length, but everything above will grow. His legs need room for his entire rear end structure to elongate, which will make him more adult-correct. If he looked correct from an adult perspective at this age, he’d be too straight as an adult.
His back length will change in relation to his height, so it’s not possible to know if he’ll have a long back, short back, etc, but I don’t see anything that says it will be inappropriate. Usually around 3 weeks, the ratios you see are pretty indicative of adult ratios for neck and back. After that, things lengthen in various stages so you lose perspective
Overall, he’s going to be pretty athletic, I see no reason he can’t do well for what you want, assuming his mind likes it.