Load Balancing ISP (How vpn/firewall Acts behind Load Balancer)

Dear All I have 2*Force point Firewall connected work as cluster and connected to switch with 3 ISP routers &The force Point make VPN connection to 3 Remote site through using 3 ISP ( 3 Tunnel per Remote site ), in same time i have Video conference system inside my local network with destination nat and H323 policy to allow h323 Call from outside, the inetrnal user use nat overload to access internet . i want to use 2 BIG-IP ltm to balance internet from internal client over 3 isp " All with real ip". what if i put the f5 " with The Puplic IP ", how i can manage VPN connection as it need public IPs on Force Point Cluster which will be reused on F5 appliances , Video conference & Internal User access