It would be great to have a custom field that can be backed up by a list of values derived from column(s) in a database table. Ideally when you are adding the field you would be asked for driver/connection details or a jndi reference.

You could then just type the sql statement to select the values for a drop down list. You would need to tell the field which is the key to store and what is it's display name. When a value is selected, its key is stored.

This would open up Jira to all manner of new possibilities.