iRule to Change Default Pool (not redirect to another pool)?

After working with an F5 consultant in regards to my questions, I have the following results for my questions:
1. Because there are still active nodes being referenced in the iRule (even though they aren't being accessed per my variable), the Virtual Server will still be marked as "UP", even though all nodes in the current production pool may be down.
2. An iRule cannot change the Default Pool for a Virtual Server. This will need to be done through an API call.

Thank you to everyone who contributed to this thread!