I don't know if this is a good idea or not. I can think of different scenarios.
BUT I must say that there should be a way to reward a team that doesn't suck and keeps the same players. Currently when you don't trade, the fans are happy because you don't trade and at the same time unhappy because you don't do everything you can to win. I don't totally like that.
Now, if you always have the same team and you are bad, then I don't see a reward there. People get bored and the team clearly doesn't have good chemistry.
My point is, I think you have a good idea there. Probably needs more work, more discussions to reach the optimal solution. But at the end of the day, I do think that continuously decent results with the same team should definitely incur in some additional plus for the team.