Additional important reasons not to use /ssg/ping for your load balancer health check:
This service runs in the apache layer, which means it can be up with the ssg service is not, giving the load balancer a false impression that the gateway is ready to accept traffic.
Typically you want the health check on the same port as services, which means the /ssg/ping service would be exposed to clients, and therefore they can identify (by it's existance) that you are running a CA API Gateway (anonymity and obfuscation are your first line of defense).
The /ssg/ping service is useful for diagnostics and troubleshooting, which requires that password mode be enabled, however load balancers usually require that it be in ananymous mode (and if not in anonymous then the account used by the load balancers might lock resulting in the services being unavailable).
(And of course, it can't do what you are trying to, which Chris outlined how.)