If you dont swap players often then the star players section in the fan survey goes up and that in one way can be seen as just what your asking for. If you sell players once that has been in your club longer will decrease this section more then those that has only been in the club for a short while or not had an important role.
I sold a rookie draftee (who never played) last week, and my merch took a $1K hit. I was a bit surprised as my overall fan survey had actually increased from week to week, so either that rookie was truly worth $1K to my merch, or some balls are worth more than others in the fan survey when it comes to determining merch. Probably a combination of both factors. I'm going to start tracking my fan survey.