In regards to the Z position, I'm guessing you want this to tell you what's in front of what? You will want the Z position of the center of the drawn geometry instead, and there can be several draw calls per panel, so that's not as simple as that.
The copy/paste is a good suggestion, thanks.
Muli-object editing is a Unity 3.5+ feature, and NGUI is currently supporting Unity 3.4.2. I've also looked into what's needed to get multi-object editing working and it required some pretty extensive changes from what I saw. I can't promise this soon.
