Hi
I did a longer, maybe better reply, but it didn't save and I lost it all!
I am suggesting using Select Dynamic Field.
Main Content Type
"Object: Article"
"Title: Main Content Type"
"Name: main_content_type"
Repeating Content Type
"Object: User"
"Title: Repeating Content Type"
"Name: repeating_content_type"
Add Select Dynamic Field to the Repeating Content Type.
"Title: Add User Name"
"Name: add_user_name"
"Query: Construction"
"Table: #__users"
"Options Name: name" // Gets User Name
"Options Value: id" // Stores the users id
"Storage: Format / Object: NONE"
Add GroupX field to the Main Content Type.
"Content Type (form) *: Repeating Content Type"
"Storage: Format / Object: CUSTOM | Article | user_list[repeating_content_type] // create the db column you want to store the info in, and mention the field that will collect the data
Might be helpful, might not..
If you know how to do the auto complete bit that you mentioned let me know, please
Bucklash