Jimmie Reynoso
Signed as 21-year-old S14. As you can see, despite Makeup of 3, his splits, Durability, and patience developed pretty well, while everything else was just a point here, a point there.
The development pattern is a little strange, compared to, say, a draftee at age 21. For example, his vsL split developed 0 points in his half-season after signing, then just 2 points in his first full season. But it developed an additional 5 points in subsequent seasons.
And despite fairly minimal progression from S15-S16, several categories did not finish developing until Spring Training S19 (Dur, Pat, vsR).
Also, the normal pattern of development for batting/fielding ratings seems to be turned on its head here. Usually, I expect batting ratings to stop developing completely while defensive ratings are still progressing a point here, a point there for another season or 2. This tends to be true for both drafted and 18-year-old IFA players. But you can see that Reynoso's defensive improvements are smaller, and weighted earlier into his career, than his batting improvements.
So I think there won't be a ton of development from your guy, but I wouldn't be surprised to see him continue to pick up a point here, a point there for several seasons to come.