Welcome! I only read your post so I apologize if I am repeating something.
It's pretty hard to try to figure out where his best fit would be right now as a 2020, but the time is right for starting the search.
First, it is my belief and understanding that D1 programs that continually and consistently compete for the championship, recruit baseball players. That's just the way it is.
If you went for a job, you wouldn't tell anyone you would work for free, why would anyone indicate to any coach they would join the team for nothing? That should never be disclosed unless that is the only option the player is given.
As you are aware D1 only allows 27 athletic scholarships, if they fully fund, but you mentioned something very interesting.
If you and your wife have attended and are regular alumni givers, many programs have money set aside for that purpose. I am not sure of the particulars but you might do some research. Attend camp and do get to know that at one point and that maybe a way to find his way onto the team, though he still has to continue to improve to the best of his ability on the field and in the classroom.