Root user privileges are identified with
uid 0.
You can modify another user's uid with
pw usermod <user> -u 0 (you should consult
man pw and verify this first).
However, those users will partially messed up and this setup is fragile.
BTW there is already a default "root clone" called
toor (with uid 0).
There is a documentation page about
toor:
[Only registered and activated users can see links. Click Here To Register...]
My advice is to rather use the
su or
sudo utility, add your unprivileged user to the
wheel group, and gain root or toor privileges whenever you need it.
It is a general recommendation (no reference now) to only escalate to root privileges when absolutely necessary. A lot of bad things can happen - accidentally or on purpose - and with the root user, there is no barrier or second chance.
Just think about what happens if you do
rm -rf / or if you delete/change any other critical data. This can not happen if you use an unprivileged account.