Unfortunately that's a no as well. iRules are purely a data-plane engine. adding/deleting pool members is a control-plane function and that is handled from external processes like the GUI or iControl apps. Now, you can make a data-plane decision by sending traffic to/from certain pools or members within a pool, but you can't add/remove directly.
But, you could do something like I mentioned before where you log a message to the syslog system and have a monitoring process look for certain messages and then perform the actions based on those messages with a shell command.
-Joe
Nimbostratus