Wants configure with two Gateways in F5 to access remote users.

The first question would be: is the deployment inline L3, or just one/two/multi-arm deployment with SNAT? If the latter, then you should just verify that auto last hop is in place and the services should run respond fine without any other configuration changes as long as the new gateway is on the same VIP VLAN as the old one.

If its an inline L3 deployment, you would probably have to look into PBR. Another option could be route domains (Cisco VRF), but as you state you are using APM you should test this first as not all APM functions perform as well with route domains (alot of services used by APM rely on the default route domain).