You can also already preemptively go through the opt out flow in developer options. It's a little annoying but not particularly more than the toggle you already need to flip to enable third party app installers. Once enabled, whenever Google chooses to flip the switch it won't impact you. I'd never consider using out of date software when it's ultimately still possible to both install unverified third party software and have the latest software updates.

Far too many apps rely on Google play services for fully disabling it to be an acceptable solution in my opinion.