Research on how to create a virtual DMZ with Mutli-WAN (Multiple Internet Connections) for Inbound and Outband traffic.
The theory is that a user will hit a url called https://access.* which will have multiply A records pointing Public IP Address that are provided by different Internet Service Providers with NAT to the Datacenter Router, that are forwarded to virtual VIF. Setup a Subdomain with a HTML forwarder to a Dynamic DNS or Public IP address.
Reference Active/Active Design