On opening the context menu for a file and chosing "open with" the requester could have 2 tabs: one as file requester and the other as choseable icon or list view of preset applications. Would be a shortcut for often used apps which shall be used for different kinds of files without setting them in the filetype editor. Any app/script should be DNDpable here and add a new list entry/icon place. Drag your mediaplayer or image viewer inside this icon view and from then on you can easily open any file with that whenever you want.