My son was very similar to yours in many ways, travel coaches said "could be mid-major" as a pitcher, got some interest, but he had a lot of D3 love as a 2-way. He went to a D3, has been on the field since freshman year (although not 2-way for most of it), with good summer leagues.
How is this gap year program, playing against D2, D3, juco, going to show that he can be D1, especially as a hitter? JUCO would do that better, I would think - he has to face D1-type pitching. If he's a D1 prospect, why is he afraid he wouldn't get playing time at a JUCO?