Checking if Virtual Server disabled within iRule

The problem I think is the iRule can't distinguish between disabled and down members. Remember, if it's an issue of all pool members being down, I would like to display a FailWhale page so the user understand that this is a service issue, not something that was planned. On Citrix Netscaler, you'd use the "-backupVServer" option on the Content Switched server to point to maintenance page, and then the FailWhale vServer for the LB vservers