First of all, I am not going to enter the discussion where the loudest win the conversation.
I do not really know who you think you are opening the market as you are trying to impose more taxes. That would end up that all managers will either be even or lose money except the owner who drafted the player ("When you buy a player the price you bought him for is your max return should you ever sell him").
It is natural for me that most people are losing money on the market. It is one-zero game for buyers and sellers. You either make better bet than your rival or you lose same amount of money that is equal to gain of counterpart. You just can not make it a place where everybody wins.
I am still hardly see what you are trying to achieve. Getting rid of taxes? I am fine with that, however it is suppose to mimic agent fees from real world. On the other hand, 3% tax is not much.
Currently, there are two limitations: above said 3% tax and player holding period. It does not sound as a huge problem. All else you are trying to imply has nothing to do with this. Market is not trashed, it is rather sheep herd movement a problem.