You need to be careful with lockstep compensation plans. Your high, and even mid, employees will resent that low performers are getting the same as they are.
Most places I’ve worked had some concept of an “expected raise”: 1-3% a year. What I’m suggesting is making that a bit steeper and still paying performance-based raises on top of that. (I’m not sure what exact numbers make sense here: maybe a total of 10-20% expected raise over the salary offer + up to 10% based on performance?): the goal here is to save money by reducing the amount of domain and operational knowledge that just walks out the door.