If you make it 18 year terms and stagger the appointments (as grandfathered-in justices die or retire) to every 2 years, you can make it so that each presidential term appoints two justices, which at least removes some of the potential for luck to dramatically shift the balance of the court.

If that were the case, and justices' terms started in January of even years (to avoid the election cycle), we would currently have 2 Trump appointees, 4 Obama appointees, and 3 Bush appointees, roughly matching what the balance of the court would be next month if Ginsburg had died 3 months later.