Spec. Role members into reg. form dropdown

Dear UM support Team!

I’d like to ask some help with the registration form dropdown field. Is it possible to insert this fild automaticaly (maybe with a shortcode or hook) the users name, who have a specific role like: Leaders? After we switch the roles on admin board, we’d like to insert the new leaders name put into the registration form dropdown.

I made before manually a snippet with his names in dropdown callback, and on the registration mail shows all well. In this case , if we modify this, will works well?

Thank you in advance
Roli