I just uploaded a new "NewLayout" build for the Mac. This gets the new Layout tab pretty close to feature complete. You can add models (click on the button in the toolbar and then click/drag where you want it), copy/cut/paste models using normal cmd-x/c/v, you can do some filtering of what is displayed, etc..
There is also a couple other new things:
1) Candy Cane model (from Keith)
2) Window frames can have 0 node on the bottom.

Anyway, if you could give it a try and see if the work flow is usable, that would be great.
Thanks!
Dan