It'll be useful to be able to change the "view type" (shared, contains documents not in any folder, private...) of existing views, so to folder.
Below is the scenario which triggered this thought:
I'm customizing my mail. The "Mail Threads" view can help to organize the fast growing mail and let me see the context. But it's not like the Inbox, which I can move a mail to other folders. I want to change the view to exclude documents in other folder.
I think other type transfer will be usful too.
I can compare the flags of different type of views and write some script to manage it although.