What do you think about "special training"... Paying fixed amount for special trainer that would raise player potential?
Lets say solo 1v1 training with Jordan. Tips that Jordan will provide to your player will have huge impact to his career.
Paying:
1k to get player potential from 1->2,
2k to get player potential from 2->3,
4k to get player potential from 3->4,
8k to get player potential from 4->5,
16k to get player potential from 5->6,
32k to get player potential from 6->7,
64k to get player potential from 7->8,
128k to get player potential from 8->9,
256k to get player potential from 9->10,
512k to get player potential from 10->11.
Each week you could only raise player potential by 1 point... This could fix some problems for new players (easier to obtain player to train) and old players (market price drop).
Just to keep it fair... You could only raise potential to players that are gonna be drafted after change would be implemented.