I agree it's an interesting concept.
If a potential participant was otherwise comfortable with the idea, I'd advise him/her to be careful because Pando (or another organization trying something similar) might not be around years from now when one of these arrangements was due to pay off. The underlying contracts would still be enforceable if they were written halfway competently, but each member of the pool would be faced with trying to track down other members and potentially serving and suing them. That would be expensive. For that matter, even if Pando survives, its interest is in getting its percentage off the top--I doubt it would have a fiduciary obligation to make sure pool members also get paid. A lawsuit against Pando could be successful, but again would be costly, and Pando may not have enough assets to make a suit worthwhile. You are dealing with a company and a model that has no track record. I'd feel much better if this were offered by an existing insurance company or maybe an investment bank. (And if people show interest in this kind of thing, maybe that will happen.)
Participants also would want to know who the other members of the pool were going to be. You wouldn't want to be the highest-rated prospect in a pool, and no one would want you to be the lowest-rated in theirs. I guess Pando could guarantee participants would have some minimum rating by Baseball America or another third party scouting service--but I have no idea how much faith one should place in those.