A successful response to a monitors would mark the pool member back up. If the application isn't stateful and you're very concerned about failed responses, you could configure a monitor with an interval of 5 seconds and a timeout of 6 seconds. Then set the pool's action on service down to reselect. Anyone have concerns/suggestions on this idea?
Else, if you want to retry the request to a new server it looks like the alternative is to manually save every request and use HTTP::retry and LB::down in HTTP_RESPONSE when a response code you don't like is seen. To handle POST requests, you would need to collect every request using HTTP::collect. I could see it getting very resource intensive to use this approach.
Aaron