While it is physically possible to map multiple fields in Aha! to a single field in Rally/JIRA etc., it is not clear to the user what this will do.
Please add a warning that this configuration will result in multiple conflicting updates to that external field (latest update is always applied).
Thank you for the idea. Given the low volume of support for this idea, we do not have plans to make updates in this area at this time. We hope you can understand.