Having dealt with tryouts at a much lower level I know that there is an amount of "well I know that player can do better than he did today" that can factor into anyone's evaluation. You may really like a player and because you know him and/or his character you rate him higher; whereas, I may not know or like that same player as much and rate what I saw. Like was pointed out in the other topic w/ Memorial - you know the players that were cut based on seeing them over 2 years and 80+ games. If the (new?) Memorial coach doesn't know the players and they have a bad tryout, then his point of reference is the 3-5 days of evaluation where the primary focus is picking a Varsity roster. Those JV and Freshman players may not get the same look - I don't know. It's kind of tough to compare. One of my kids learned a valuable lesson one year in a basketball tryout about making yourself stick out and not take anything for granted. You may think you're better than someone else, but if that player did something to stand out to the coach who was trying to fill out his roster, then he'll make the team and you're cut. On any given roster there's 'outstanding', 'above average', and 'specialty' talent and 100% of those cut think they're better than anyone but the outstanding players.
All that said being able to take "statistical" data to help make comparisons as well as "emotional" data in order to evaluate any given player against his peers does seem to be a very reasonable methodology for how the GSBA fall teams were selected. Communicating all that to the parent/player is extraordinary. If people don't like the process, they are free to start their own league and face the same issues... Over time I would guess you can develop a system where player ratings based on some percentage of each set of data can rate the players 1...n. Does it exclude players - sure, but there's only so many spots available. Could a player be included that perhaps doesn't deserve it - not likely - mainly because there's too many factors. Of course there's always the axioms "it's not what you know, but who you know" and "be careful of what bridges you burn because some day you many need to cross one of those bridges"....
This is going to be very entertaining discussion (I hope)!