Thank you very much for all your work on this six year old device. It's awesome!Don't worry, I understand your point however there is no way to fix the bugs caused by old drivers on a new Android version. We don't have any reference nvidia device on a 3.18 kernel. Aside from that there is ALOT of nvidia specific stuff missing in the google kernel so newer drivers can never be swapped between the nvidia and google kernel.
It's alot easier developing for Qualcomm devices as many brands release phones with the same chip and newer drivers. They can switch out the drivers, we can't.
In short, we fix what we can fix. Aside from that, I still have hope in the 4.9 kernel so that makes putting tons of work in our old 3.18 kernel useless.
Android 12 is also a question mark as I'm getting errors related to the GPU drivers so I dont know yet if it will be fixable or not.
An early Lineage OS for Android 12 build is running rather well on my Pixel C right now so I suspect it'll be fine. I actually have fewer app redraws than I experienced on LOS for A11.