First off, big ups on the beta, I'm loving it!
I do have a suggestion:
I would love (and haven't found) a way to create master pages with layers that you can place around the page's content.
I know I can currently treat the master page content as a layer and put stuff on top of below, and copy/paste stuff out of it to appear above the content (copy, not drag as that alters the master page).
I'd like to create a master page with two layers: a layer that defaults on top of the page content (where I can put watermark-like content) and a layer that defaults below of the content (where I can put stuff that may be obfuscated with page content, like the master defaults to now).