I don't know if that was already proposed or not. But 2 little options could be very useful for transfers and loans.

For transfers first, that would be nice to be able to block the transfer to directs opponents. Like for example I'm in the first French league so I could set before starting the transfer that I don't want this player to be sold to a team from my division. In the aim not to make our opponents stronger.

And for loans, it would be very interesting to be able to validate or not a loan. I'm totally open to loan my young players but only if its to play. What's for to let him go somewhere he will not play? So justo having sometimes to discuss with the manager to be able to decide, one of my player went to a botteam and I'm not even sure he will play more than if he stayed with me.

The problem with confirming loans is that new players wouldn't have a chance to loan players. If you can choose you'd want a team that is likely to get far in the cup and maybe even plays champions league.

It would favor the strong teams in weak continents, and they aren't the ones that really need help.

I'm not so sure, for example I would prefer to loan my young players to new players arriving in league 4 or 5, than to a better team who just want more players as substitutes. Because my aim in loaning players is that they play as much as they can in the team they go. So for this, being able to discuss with the coach who wants them can help, and also not letting the player go in too strong teams.

It's also not so easy to loan players. For example, we discussed with 2 players about a loan of one of my players. They made an offer and I accepted both. We tried 2 times, but both time the player didn't want to go ;)

And what do you think about the transfers blocked to rivals?

I like the transfer blocked for rivals thing, you could pick the teams you don't want to buy, but there would have to be a limit or else it would open the window to cheating. It is realistic as well.

Limit could simply be set to "not to loan in my league" or "not to loan in my country"
That should cover most cases for a start.

I agree with TONTONKAL :) These 2 options would very nice.

When I sell players, if these are not important players, I don't really mind if it's a team from my league or my country which buy them. But if I decide to sell my best players, I wouldn't like them to finish in one of my rivals' team.

I prefer an open market, as it is now. We don't like to strengthen our main local rivals, but thats the risk you take when you list a player for sale.

maybe add a block loan option just if player isn't the best keeper/1-4 defender/1-4 midefilder/1-2 forward.

I understand the fear of strengthen your opponent but that's part of the game.
It can maybe become a good relationship between 2 managers instead of rivalry. I sold a young talented GK to a "rival" because he didn't find a GK. We have contact by message. I sold him my GK and strengthen him. In a few matches I will play against him. Maybe he can help me some time. Maybe not, but it's also a world of making contacts and agreements/handshakes.