We don't need to stop at 4, we should add 10, or 14, or 20. The more the merrier, the more the fairer. They don't all have to be appointed immediately either, they can be staggered appointments. But with a large number it would be much harder for any partisan side to gain a consistent advantage decade after decade.
And lifetime appointments should be ended as well.
But, as America stands today, it ain't hapnin'. Corporations and the super rich have a lock on the politics of this country, and they won't be giving it up. And the people who could make the changes are too polarized to mount any serious opposition.
I will say what I have said before, the only realistic solution is to end the federation, and allow like-minded states to reformulate into new nations. Short of that, our only choice is to withdraw the consent of the governed, and ignore rulings of the SCOTUS.