Multi tenancy probelm at authenticating different customers

we have F5 5000 replaced at ISP to do web filtering and content filtering , where we want to use it for multi tenancy. we will divide the F5 for logical partitions each for separate customer to manage. each customer will have its own pool of AUTHENTICATION for its employees. now the problem is:- HOW THE F5 CAN differentiate BETWEEN USERS FROM DIFFERENT CUSTOMERS AND ASSIGN EACH CUSTOMER WITH ITS PARTITION? NOTE THAT THE ISP DO NOT WANT TO USE STATIC IPs FOR ITS CUSTOMERS.

CAN WE USE DIFFERENT VLANS AT THE EXRTERNAL PORTS AND BIND EACH VLAN TO SPECIFIED PARTITION (LIKE VRF IN NETWORK ENVIROMENT)