interesting ideas, but to equal things out they would need to add that component to players involved in trades and FA. For instance a FA gets a big contract and decides to take it easy or a player involved in a trade doesn't adjust well to his new location or teammates so their skill set declines 20 - 30 points. The more you spent on advanced scouting the more accurate you would be in these predictions.
Also apply to medical and training budgets. for instance some players don't respond to the extra training or therapy involved with teams with high training budgets because they feel they are being rushed back or controlled by the franchise creating discord with the player and thus his skill set diminishes. Maybe tie that to makeup and temper.