It would take quite a bit of work in order to bring this up to speed and to "fill out" the new windows to match the look. Not saying that its impossible, but would take someone who was rather commited... and if they had to first learn all about UI creation/modification it would take even more time and commitment.
However, the other day I saw this other UI posted in the new section and its looks pretty good (though I have not used it myself) and seems to have a similiar "leaf" theme to it.
It can be found here:
http://eq2interface.com/downloads/fileinfo.php?id=4231
If you really liked some of the windows that do work from the old nature_ui, you could install those on top of the one above and get a nice mixture of leafs and things...
Anyhow just a thought..