Me neither :-(
For a while, I thought a windicator would work, but I can't think of a relevant status that covers the use cases of the menu.... other than a "tools" icon, which isn't status at all.
Functionally, I think a windicator would work just fine (it's a menu on the window decoration, just what the doctor ordered). But it would really be messing with the concept, and likely to lead to all sorts of abuse if encouraged.
However, in 10.10 Netbook Edition, with Unity, we're already making menus much less visible by hiding them under the window title in the panel unless invoked with mouse or Alt. That's for the maximised browser window case, which is I think the one where the user is most concerned with pixel efficiency.
How about if we start with that?
Mark