Chemistry is still not on the game. A simple reduction of the GS for the new players wont cut it, IMO.
So, heres another simple suggestion that may drive a lot of team to retain players longer.
My Suggestion:
If a player will be able to play for the team for a whole year, he can now reach 10 in GS.
Playing Whole Year with a team means (example) Player A was bought on Week 3, on the Week 3 of next season if he will be kept, he already reach that one year mark.
This is a very simple way but good enough to drive a lot of GMs to build their team away from the TM. Having a team with five players being at 10 GS will surely be salary efficient.