Unfortunately, both the target and the buff functionality are hard coded in to the target window, you can't add either to another piece.
However, you can give the appearance of separate windows if you're prepared to live with buffs that you can't move. Have a look at my target window for an example of a 'separate' floating buff window. There's also a bit of a discussion on that page about how to move the buffs elsewhere on the screen:
http://www.eqinterface.com/download....php?s=&id=5348
Myx