Occasionally a team might take a low A pitcher in the rule 5 draft because it is fairly easy to "hide" an extra pitcher in the bull pen. But in these days of the 5 or even 4 man bench, it would be difficult for most teams to have someone like that on the bench the entire year.
Baez is not a meaningless prospect, but neither is he a great loss at this point. In order to roster him, we would probably have to lose someone that we consider more valuable.
He might have some value as a second piece in a trade this winter after the draft is over, but I don't think I would add him to the 40 man roster this year.