Performing redirect in function of host

Have you tested it ? This is the best way to find if something is not working.

After that you can just try the "ACCESS_POLICY_AGENT_EVENT" to trigger an irule event. First you may need to save the HTTP::host to a variable in the "HTTP_REQUEST" event as I do not renember if the HTTP::host can be used directly in the "ACCESS_POLICY_AGENT_EVENT"  but testing this will tell you the answer.

https://clouddocs.f5.com/api/irules/HTTP__host.html

https://clouddocs.f5.com/api/irules/ACCESS_POLICY_AGENT_EVENT.html

https://clouddocs.f5.com/api/irules/ACCESS__policy.html

Also this post is nice as it seems like your usercase, so sometimes when you google for previous posts you will find answer even without asking:

https://community.f5.com/t5/technical-forum/apm-policy-based-on-http-host-header/td-p/206460