My feedback is that it seems a risky move. Not just for baseball reasons. A lot can happen in one year, you never know. I've seen some kids work a year and for a multitude of reasons, not end up going the second year.
Most of my sons classmates didn't know what they wanted as a major, I think that's normal. The freshman year is all generals anyway.
You state he won't make all that much money anyway, and that doesn't seem to be a big issue.
He'll still be "trying to find himself" at 19 instead of 18.
It generally takes 5 years these days for a college athlete to finish a degree, in your senerio it will be 6.
How will he feel about staying behind a year when his peers are heading off.....does that even matter?
If he's getting interest for ball now, it will be hard to watch others fill his potential roster spot. Will he fall off the radar, possibly.
Last of all...what does HE want to do?