Did you find an answer to this? I was thinking of creating the same setup to make new releases/deployments un-noticeable to the user.
No solution yet I'm afraid.
The only work around I have is to change the jk properties to not point at the jboss you want to take down and then restart apache, take down the server, make your changes, bring the server back up change the jk properties and restart apache again.
So not really a useful solution at all.
With 3.2.5+ the startup/shutdown of the connectors is seperated from the deployment of the web apps. You can also stop/start the connectors through the jmx console/mbean server so you can take down the transport layer, redeploy the war and then bring backup the transport layer.