I just revisited this issue and that plugin appears to be what I need. I ended up writing sqlstatements to change the existing User Picker field to the new type, and then to change all the special 'reporter' values to the actual user that reported the issue. I will include them here in case there is someone else out there in the same situation as me that would benefit from it.
Keep in mind this was already a user picker and was a required field so all the data in there was already appropriate for the new field type.
First sql statement changed the custom field type:
update customfield set CUSTOMFIELDTYPEKEY='com.sungard.jira.plugin.currentuser:currentuser', CUSTOMFIELDSEARCHERKEY='com.sungard.jira.plugin.currentuser:currentuserpickergroupsearcher' where cfname='Tester'
Second sql statement changed the special 'reporter' user we were using to the actual reporter:
update customfieldvalue As cfv, jiraissue As ji SET cfv.stringvalue=ji.reporter WHERE cfv.issue = ji.id AND cfv.customfield=(select id from customfield where cfname='Tester') AND cfv.stringvalue='reporter'
It is best to do this while jira is shutdown, and I believe a re-index is mandatory once it is brought back up.
I used http://confluence.atlassian.com/display/JIRA/Database+Schema and http://confluence.atlassian.com/display/JIRA/Changing+Custom+Field+Types as references.
Thanks for writing this plugin, it is incredibly useful.
I still think this would be a reasonable feature to have in the base product, but that is just one guy's opinion.
Thanks for taking the time to raise this issue.
Due to the large volume of JIRA feature suggestions, we have to prioritise our development efforts. In part, that means concentrating on those issues that resonate the most with our users.
I am writing this note to advise you, that we have decided to close your Suggestion as it has not gained traction on jira.atlassian.com. We believe being upfront and direct with you will assist you in your decision making rather than believing Atlassian will eventually address this issue.
Thank you again for your suggestion and if you have any concerns or question, please don’t hesitate to email me.
Kind Regards,
Kerrod Williams
JIRA Product Management
kerrod.williams at atlassian dot com