From what I have heard, many people like fact that we give sellers their money immediately, rather than making them wait until the end of the auction. They are guaranteed that money, so there is little reason to make them wait.
Your first point is about managers bidding on their own players. This does happen. In fact, almost 2% of all transfers are purchased by the seller. If a seller is bidding against you, it may mean that they are not serious about trying to sell their player. For you, it should be no different than bidding against any other buyer; you can stop bidding any time. In the end, routinely bidding on your own players is a bad strategy. When a seller ends up buying their own players, they pay a fee of at least 3%, and the fees for that player's next sale player immediately jump to 20% (or higher, if they have made many recent sales). Sellers who are not willing to sell their players for under a particular price are much better off if they just set a minimum price when they list the player.
Your second point is about the effect that managers buying their own players for inflated prices could have on the new precio estimado de transferencia. This is a very good point. Since you pointed this out, we have excluded all of these transfers from the data used for the estimates. This has already taken effect. Thanks.