Fun ideas, some already said:
Staffing over 100% at low level facilities and facilities with historically high turnover rates. If 15 people want to transfer and facility staffing will only ever be 85%, then the current system is will not work.
High 3 based off of actual earnings.
EV chargers at all facilities.
Shorter shifts and/or shorter work weeks. 4/8s or 5 6 hour shifts on a rotating schedule would be a lot easier on the body than 6/8s. On the same line of thinking - overtime after 32 hours.
More admin time, health and wellness leave, detail days that can be worked remotely (give employees a day every couple months where they have to complete a couple of hours of elms, and don't make them come into work).
Time off awards when Admin staff get early holidays but staffing doesn't permit controllers to take the same hours off.
Transfer process where you can apply and be considered for one facility at a time - be given an approval/denial within 3 months and an offer letter with a definite start date no more than 4 years in the future, with specific reasons given for release dates over 2 years (4 because regardless of the facility type or level, that is enough time to put out a job bid, hire, and train a replacement employee). Avoids shotgunning, line skipping, and agency excuses.
Retirement based off of hours worked instead of years worked.
If you've worked 20 years of 50 hour work weeks, that would be the equivalent hours of 25 years FT.
More willingness from management to implement TMI in line with our actual operational readiness. Too often, the system is expected to work 100% of normal traffic volume or more with 75% staffing. It's an unreasonable request, and the front line controllers make it work when traffic management and command center don't do their jobs correctly.