I wonder if these unsigned guys wouldn't be better off waiting until after the draft to sign where attached comp goes away.
Think about it this way - teams spend millions of prospect capital to bring in needed help at the All-Star break (and before and after).
If a few of the high profile agents pulled together and got a field in Florida where their clients could play and keep sharp, then they may actually get their clients a better contract by waiting. You have basically three areas to draw from - the high end who aren't getting the contracts they think they deserve (Arrieta, Moustakas, Lynn, Cobb, etc.), the veteran guys with injury/performance concerns (Anderson, Melky Cabrera, Yunel Escobar, Clippard, Coghlan, Collmenter, Dickey, Duda, etc.) and the guys who are likely to only get a ST invite anyway and likely end up on some AAA team.
It would be like a developmental league for stars and injury rehabbers and AAAA last chancers.
The risk to the player (say a guy like Arrieta) is that he performs badly and ends up with a worse contract and/or he gets injured.
The concept is a bit like what Clemens did a few years ago but for different reasons.