From the above description i understand that you only want to use multiple gateway so that you can have different authentication profile for different users
If you have used one ip adderss as your gateway you will not be able to call the same ip address again to create a gateway again.
# One solution for your requirement is to use Authentication Sequence.
# Call multiple auth profile in authentication sequence and call this auth sequen under your gateway( in place of auth profile )
some details for auth sequence
In some environments, user accounts reside in multiple directories (for example, local database, LDAP, and RADIUS). An authentication sequence is a set of authentication profiles that the Palo Alto Networks device tries to use for authenticating users when they log in. The device tries the profiles sequentially from the top of the list to the bottom—applying the authentication, Kerberos single sign-on, allows list, and account lockout values for each—until one profile successfully authenticates the user. The device only denies access if all profiles in the sequence fail to authenticate.
I hope this may fulfil you requirements
... View more