Just some thoughs:
1) Not many people would be able to afford that, so only the richest team get the benefit
2) While it would help with some inflation (barely any in my opinion) it would provide more great players into the market and somewhat reduce their cost
3) Because of number 2 it would not be ever financially legit to do this and would somewhat hurt smaller teams
Overall, it's a no to me. I like the current training system, would like to see some changes, but in a different manner.