My main problem with your idea is, that you think training must be worth it's cost, when actually the price of training is modified by the supply and demand at the transfer list.
I agree that setting a higher initial price for FA's was a good move by the BB's. I just don't understand why would you feel the need of upping the value from 10x salary. There are already a lot of players that do not sell for 1mil. 10x salary works well, because the one dimensional players, who usually have a higher salary because of it, will not sell and multiskilled players usually sell at higher value. Surely you are not saying the equally trained SF's get sold cheap are you?
I think the BBs want a balance, equilibrium etc.
Getting closer to equilibrium, means lesser and lesser free funds in the system. Therefore it's hard to imagine prices going up when there is less free money in the mix. With your suggestion it would be mostly the same as removing FA's all together. I think the current 10x salary is good enough a solution for now.