The problem with training peripherals early is that u21 is such a sprint, by spending time on the (slow-to-train) guard skills, big men are going to be throughly outclassed inside. For the NT it's not as much of an issue because NT big men tend to have kind of stabilized inside, so the differences in core skills tend not to be as huge. A 12/12/12 big man on the u21 team is going to get owned. And he's going to be so far from NT level inside skills, that I'm not sure he'd really be able to catch up.
Absolutely, I totally understand that's the catch. If we focus on adding some guard skills we will be going into U21 with 12/12/12 bigs, and the competition will be stocked with 16/16/16's. I completely understand there's no getting around that. In fact it's the fundamental change I'm asking to make in how we run things. My argument though is that:
1) Maybe our big men will be able to beat their big men outside/midrange, and what seemed like an advantage for our opponents will actually be mostly a wash for us?
2) Either way, those guard skills will pay off at the NT level once our guys catch up on the inside skills around 24-25. And I do think our guys could catch up: if we have five seasons (20,21,22,23,24), good height, and we're one-position training only 3 skills (I think we ought to consider SB'ing too but that's a whole different conversation) which mostly also cross-train each other, that's 4x IS, 4x ID, 4x Rb each season while still allowing for stamina, FT, one on one, or whatever twice a year.
So even with the slow down in age, with 20 one position trains at each skill shouldn't our guys be able to go from 12 to 17-18? The advantage of running the out of position training early is that once the age effects start hitting, you're already done with guard skills and even though things are going more slowly, at least they're being trained in their natural position.
The other consideration is that any US division from NBBA to d.V could train secondaries first and then train primaries for as long as their team's success allows, while the same can't be said about training secondaries last because at that point there's a very limited number of teams who can even afford the player. So a system that encourages training secondaries last limits the number of players who will ever see secondary training.
Just for the record I want to state that I completely understand asking managers to train big men in this way carries a high risk of costing our team U21 victories. My position is that the risk (or more pessimistically, the trade-off) is worth the reward to the US community, through the benefits to both the NT and the managers who own these players.