Yeah I think this is what OS X does (or used to do), you open the menu and it does its initial refresh, and only after quite some delay of the menu being open, it refreshes again. Easy enough to choose your network in that large amount of time. I may be missing some subtle details of it though, since I haven't used it in a while >_>

This can still make that just as you click, it adds entries and makes you click the wrong entry (accidental clickjacking).