Technically, you are trying to use something that is not available, because of the limitations of an active check:
- The check performs exactly one call Monitoring Plugins - check_http
- Each active check only runs a single command
Sorry, at this point I do not see a better fix than either a wrapper or a rather simple special agent. Sure, extending active checks to iterate over all IPs and then either return, best, worst or failover (only one must be OK) would be appreciated by many users, but (I guess) less by our developers. Still, if you prefer such a solution in the long term you might propose it in the features portal: https://features.checkmk.com/