That's what https://plasma-mobile.org is supposed to be.

But the problem is there is yet to be a single device that has every hardware feature working %100...see https://wiki.postmarketos.org/wiki/Devices#Main

Right, plus it needs a better backing to make a nice UI. Plasma mobile is more of a POC, not really a polished user experience by far.

One good thing Google could do is demand upstream open drivers from hardware makers.