aiss Again, if you don't use the owner profile for your daily use, then it wouldn't be a problem. It's a simple solution. It checks most of your boxes, and, best of all, it doesn't require the devs to add any further features or make changes to the OS or Settings app.
In your OP, you mention something about police forcing people to give up their passwords. If the police are already using the methods you mentioned to force passwords out of people, then would an additional password really be a deterrent?
If someone were to steal your phone and their intent is not to steal data, just the phone, they could easily factory reset it. No password needed.
aiss Always use auxiliary users to configure files.
aiss Grapheneos needs to implement "deleting the auxiliary user configuration file" and needs to enter the password
Even if it's possible to allow a different secondary user to also modify profiles, it doesn't make sense since Owner still has to have that permission since it's the only profile on newly flashed or factory reset devices. Owner still needs that permission because secondary user profiles can be removed while Owner can't.
The only way I can see your request being fulfilled is if the Settings app were to optionally force Owner to authenticate when making certain changes, like in this guide. Depending on how they implement it, the settings app could also force authentication for other sensitive settings. But, then again, my suggestion to use a secondary profile for regular use instead of the owner profile achieves the same thing in practice.