Moving a (unlinked) clip up or down a track with a KB shortcut is a common request from a FCP editor. I used it often myself. That feature came into FCP5 or so, but now it seems like users can't live without it. I'd make a feature request for this:
http://www.adobe.com/go/wish
Kevin Monahan
Sr. Content and Community Lead
Adobe After Effects
Adobe Premiere Pro
Adobe Systems, Inc.
Follow Me on Twitter!