As DopeGhoti says, the classic way to do this is to log in as root. There is also a history of giving a second user other than
root the UID 0. This gives them the root privileges, but with their own
passwd settings e.g. password and home directory.
Modern desktop software e.g. gdm will be set up to refuse logins as root / UID 0. There may be methods to gainsay this in some cases.
Attempting to maintain full access for a user which is not UID 0, will be stymied because the permissions of system files are set according to the packages they are installed from. When you install new packages, or upgrade existing ones, it will set permissions on new files.
There will also be restrictions, e.g. on the files you don't own, you won't be able to change their mode including the executable bit.
Any daemons that rely on setuid programs would be broken.
Software which checks for sensible permissions on files containing authentication secrets or authentication configuration (e.g. sshd authorized_keys), will be broken.
It wouldn't make a lot of sense to try and do it this way.