Thanks cabbagedad.
Especially this statement of yours: "a majority of D3 schools are less inclined to look to Juco transfers," which confirms a similar impression that I had.
However, at this point, he's dead-set on D3. He's hoping for the academic challenge and diploma-cred of a "second-tier academically-strong D3", to coin a term. Maybe NAIIA is a better choice. But neither he nor his parents are currently interested in that. On the other hand, the factor you mentioned above might be the deciding factor.
You also said,
"Assuming he went straight to Juco out of HS and competed two years with no lengthy breaks, I don't think he'll find much difficulty from an athletic regulation/qualification standpoint - others can speak to this in more detail (although I do believe there are timing elements with regard to contacting other schools)."
He did in fact go JUCO straight out of HS and I assume he'll complete his second year without any breaks.
If anybody knows about the athletic regulation/qualification/timing-elements of JUCO to D3, please weigh in. Thanks!