This is only an opinion but the best way would be to use System Manager and build a template or as many as necessary then apply to your users. You can tweak the template to be exactly the way you want for each station or user type.
If you don't have System Manager you can still use the Avaya Site Administration tool to make the changes. Although you can make templates for created new stations, you can't apply them to existing ones. You can use the Find and Replace function to change the station type, and filter by station range or other criteria if you want to limit the scope of the change and not affect every station.
BUT... (there's always a but.)
Some feature buttons and programmed buttons may revert to default or become blank when changing the station type. I'd create a test station and try the change on that before committing a whole lot of changes.
I hope that helps.