My Alfresco BPM (aka Activiti) platform will start off supporting over 10,000 end users, and will eventually grow to support over 150,000 end users. As such, limiting the people search to just first and last name will not be sufficient. I'll have too many people with the same first and last name, and the returned list does not show anything other first and last name.

Does anyone know how I can extend the People field to allow my end users to search on other attributes of my users? Email address would be fantastic since that is a unique identifier and already included as an attribute of Activiti users. Or at the very least display other attributes of the returned users (such as their emails) that match the names entered in the search?
The only other alternative I've thought of is building a REST API that I can query for people based on the other attributes, return the people that match the query. Then allow the user to select the correct person and then set the People field to that person for the user. Which sounds technically feasible, but I think would require more work than extending the People field to search on other attributes or show more attributes in the returned list.
Thanks.
-Joe