Adam - in the coming release (due March 14th) we are adding support for dynamic choice lists.
This means that a project user input can be based off the values coming from a feature service field.Not only will the list reflect the latest values in the feature layer, you can apply a where clause in order to filter the returned results. For example, only show records that have a username in the user field that match the current signed in user.
Please go to ArcGIS QuickCapture if you want to test out the beta.
Thanks
John