I know of no reason why you cannot have multiple users as root (i.e. UID 0). Keep in mind that when you make a file as a user with a UID of 0 it will not display that users name of the user who created it (when you do a ls -l). As I understand it, the ownership of a file is not saved as the username (or group name as the case may be), but as the UID (or GID), so your "regular user" with a UID of 0 will create files with this UID and since the first user to translate out to the UID in the /etc/passwd file will likey be root, root will show as the owner of these files.
Also please keep in mind all of the standard warning messages that go along with extensive use of a root (UID 0) account. It is amazingly easy to do very bad things to your system in a hurry if you are not careful.