Sorry but I'm brining this thread to life!
A revolution has happened in custom ROM so... I'd no choice!
And the revolution is called:
Project Treble
Now, what exactly is Project Treble? Well, it's this (in a nutshell):

Project Treble, recently introduced with Android Oreo 8.0 is basically separates Android Framework from vendor implementations. So basically, the Android OS is separate from hardware drivers and other custom implementations made by vendors which go deep into Android System.
The benefit?
A revolution in ROM Flashing!
Here, you can see a Huawei Mate 10 (Which supports Treble) running a fully stock and almost unmodified AOSP ROM with little to no modifications:
As a matter of fact, the man made this ROM in just a few hours. And what else?
Prepare to be blown away:
This ROM is compatible with other smartphones as well such as Essential Phone, Google Pixel 1 and Honor 8 Pro etc (All Treble supported) which is INSANE because they have different hardwares. Huawei Phones have Kirin 970 (I think) Chipsets whereas Essential runs on Snapdragon 835 but this ROM works on all of them, like a charm!
And it means that 'theoretically'; one can run the same ROM on all smartphones, from an ultra-budget MT6582 to a flagship level Snapdragon 8xx provided the phones support Treble.
And if that's not a REVOLUTION then I don't know what is!
Good Day!