What should customer success managers be paid on, if anything variable at all?

I am reviewing pay for a team of 28 customer success managers at a human resources software company in Amsterdam. They are on fixed salary plus a 10% company bonus. Sales leadership wants to move them to 80/20 with variable tied to net revenue retention on their book of accounts.

The customer success director is against it. Her argument is that customers trust the team because they are not on commission, and that retention depends as much on product and support as on the manager.

Has anyone made this move, and did it change how customers were treated?