It is my experience that this is what Google does with their Pixel phones. It is really quite simple to unlock the bootloader and do whatever you want on a Google Pixel you own (i.e unlocked, no carrier). They even give you this really handy Android flash tool which uses WebUSB to fully restore your device when you mess up. Heck, custom ROMs like GrapheneOS and CalyxOS are even able to sign their own images and allow you to lock the bootloader with a non Google OS.

However, all this comes with the caveat that SafetyNet will flay you alive. The cat and mouse game with Magisk and other methods to maintain root undetected is moot when I've used apps these days that make a fuss when you have developer settings enabled. To be honest, that seems acceptable to me, I can do what I want with my device, software vendors like banks and the like have a say in how I choose to access their more convenient services. I can play nice with them if I want, even using a second phone perhaps, but I have a choice.