Improve player negotiations (transfer market between managers)

Currently, the players transferring market between managers has no sense. You can buy players (not cheap at all) which in just a few hours will loos 20% because the new season starts.
I think it would be available all season, not to limit between servers (easy now that we already can have friends across servers) and without the level effect.
For example, if a friend who is 25 level has a player with 90% average, I could buy as a 90% player even if I'm a 40 level manager. This would avoid the multi accounts players that have several accounts only to buy and sell players between accounts.