I don't know if there's any good solution to this, since all this seems to be necessary for the security model.
EDIT: Wait, isn't this what A/B partitions are for? (ie, you can brick one partition and still boot from the other) Also, shouldn't it be possible to flash an image signed with the correct keys without unlocking the bootloader and wiping the user data?
Google will not using their service for tap-to-pay.
I'm okay with losing access to Google wallet while using Graphene os (I can just use plain old credit cards), but I would like to have the option to revert it in the future.
Myself I have not reverse engineered the Titan M2 security chip, but surely it uses eFuse or OTP memory for anti rollback protection mechanisms and such.
These are really basic hardware security primitives. I'm curious why you're under the impression Pixels wouldn't use eFuse.
There's no such thing for Pixels, and it also doesn't void the manufacturer warranty.
(Google Wallet runs fine for storing cards and tickets and whatnot, you just can't pay with it)
See: github.com/chenxiaolong/avbroot