I find it funny to see these "what if" questions everywhere. So reminiscent of the silly "TOP [insert integer] [insert noun]" format...
What if CME hits Earth tomorrow? Or think about how useful an ICE car would be without very narrowly specified type of fuel to put in its tank. ("Well, if the oil companies stop producing/refining petrol, ALL of these ICEs become instantly dead!")
The project doesn't have unlimited resources, but a very specific set of goals and it is clear they considered nothing but the best. It escapes me why one would want to have a second tier device(s) included, likely compromising the sec model in 2 different ways: by diluting resources and increasing attack surface. For what?
It's like complaining that your house only can be accessed with one type of a key. ("How ironic is it, that if I lose my key, I will be s*** out of luck trying to get inside, because the lock manufacturers only decided to offer one type of a key! We must expand options to find a second rate substitute to open my door. Perhaps a plastic version from Huawei available at the local convenience and neighbors' woud help me get inside! One key type per lock is a giant elephant problem no one is willing to discuss!").
There are so many paralells. How about medical field? Say for an operation. You have to pick one doctor/team. Who in their right mind would want anything but the best-bar-none? GOS on a Pixel is that.
I fail to see any logic in OP.
In regards to going to other ROMs... I've wasted some time with two others before GOS. I didn't realize it then, but now it is very clear to me GOS eats them both for breakfast in several fundumentally important ways. Perhaps you'll realize that at aome point as well.
Either way this isn't meant to be disparaging...
Just void of sensibility to my way of seeing things.
Good luck on your journey.