Patch updates really should be auto install by default for those users (but still let users opt out manually through settings if they want). Probably on home WiFi and while charging, just like Google Play does by default.
With A/B devices, there’s no reason not to. It’s completely invisible to the user, and takes effect next time they reboot or run out of battery. Just needs maybe a single notification when it’s all done to tell the user to reboot when it’s convenient for them, or reboot overnight when the device is idle and charging. Completely transparent.