Single requisition tied to multiple candidate workflows?

Summary:

Questions about requisitions and internal vs. external candidates

Content (please ensure you mask any confidential information):

Is there any way to have a single requisition that can be used for both internal and external candidates, while associating a different candidate workflow in each case (one workflow for internal candidates, and one for external)? Also, we sometimes have external candidates try to apply for internal requisitions (the IP address restriction feature doesn't work because we have dynamic IPs). Is there a way to do something in the application form that will trigger a redirect and send them to one of our external career centers if they answer a question a certain way?