Training is already at an all time low value. The players that take you an entire year in real time to train can be bought for $100,000 any hour from the TL. Great players that take one and a half years of real time for maybe double that. Only if you are willing to lose for seasons and spend two or more real time years creating a fully rounded player is he actually worth something.
Training is the most fun part of this game but to be honest it already isn't worth it. To make an entire real time year of effort worthless.... is that really a good idea to encourage managers?
Your examples come true everyday already. The $2,000 salary 19 year old 6'11" SG with Hall of Fame potential would be worthless to most managers. But if someone spends the time and effort they can make him into Karl Malone.
Likewise every season those $5,000 salary 18 year old HoF players who are sold for millions end up with bad trainers who turn them into mediocre players worth 1/4 of what they were worth at 18 several seasons later when they should be in their prime. Sometimes it can just be because they are constanlty getting injured. Penny Hardaway.