Yes the pattern would be predictable. You would know exactly what the player's potential is if everything went smoothly for the player. However, if things did not go smoothly, it would change. What I propose is thsi. There would be variables that would alter the projection course. In other words there would be modifiers. for instance, injuries. There would be 3 modifiers: injury, recovery and duration. The modifier would be from 0 to 6.
1. Injury modifier: A player is projected at +6 for minor and major league projections, but he gets injured severely. A -6 injury alters his +6 progression to a 0 for the season. (6-6=0, yes negative numbers are possible. Players sometimes get worse following an injury, i.e. trying to pitch with a damaged shoulder causes more damage).
2. Recovery modifier: The injury has a +1 recovery rate. Add 1 point to the 0 and the players progression would now be +1 for the season. Player makeup and medical budget would have modifiers that potentially could improve or decrease the recovery rate.
3. Duration modifier: This determines how long the effects of the injury last. The duration modifier is +5 for this injury. That means the effects of this injury would last for 5 seasons. The above player who was a + 6 will now be a +1 for the next 5 seasons. Without advanced scouting I would not know this. Also with advanced scouting I would be able to see that a player who shows no progress for 2 years may be a +6 once he reaches age 24
1. Progression modifier. (0-2). Most players would follow a normal progression of: Age 18 rookie, Age 19 Lo A, Age 20 Hi A, Age 21 AA, Age 22 AAA, Age 23 AAA, Age 24 ML. Any player not at the age appropriate level will lose 1 point for each level above or below appropriate level. In other words a player promoted too soon or not in a timely fashion would lose 1 point from their progress for the season. Example a +3 would become a +2. Exceptions: High makeup players could be promoted early with 0 loss and, if makeup is high enough, potentially multiple levels. i.e. Big leagues by Age 20. You would find this out from that correspondence reports from each level i.e. AA pitching or Hi A hitting reports. They would say based on makeup that the player is able to be promoted..Low makeup players would lose 2 points on projection from early promotion.
2. Demotion modifier. All players would lose 1 point from demotion at any level. More points for multiple levels. i.e. AAA to Hi A would be 2 points. A high makeup player could be demoted with 0 alteration a Low makeup player with 2 point loss.
3. Duration modifier: Depending on the makeup the effects would last from 1 to 3 seasons. The higher the makeup the less the variation as per above. This would account for things such as loss of confidence, development of poor work habits due to discouragement etc. Example. I have a 24 year old who is a +6. First of all without advanced scouting I would not know this so there is a chance he would be a rule 5 draft pick. Secondly, If he did survive rule 5 draft He would lose 1 point off his progression for potentially 3 years.This would also prevent stockpiling players in the minors because they would lose progression points for each year in the minors.
Without advanced scouting I would not know any of this. Also there would now need to be quality coaches at every level. You couldn't just promote to the level of the highest coach.
There would also be modifiers for player/coach interactions, but I haven't had a chance to work on these numbers yet. For instance a bad pitching coach may lower a pitchers progress 1 point, whereas a great pitching coach could raise it 1 level. There would also be modifiers for player temper and makeup vs. coaching discipline and patience. i.e. a low temper player with low makeup paired with a bench coach with high patience and low temper may not push himself. All of the above would also have a duration of 1-3 years which you would not know without advanced scouting. Once again quality of coaches at every level would matter.
In summary just because you knew exactly what a player can be does not mean you would know exactly where that player will be.