It's a good idea that would be really helpful for users with lower display resolutions. However, there are some serious gotchas.
The system for inserting application-specific menu items, which are known as status items, is a bit "tacked onto" Mac OS X as it is, with noticeable behavioral differences between "regular" menu items on the left side of the menubar, menu extras (time & date, user switching, displays, etc.) on the right, and status items sandwiched in between. The public documentation for status items doesn't describe any way to manipulate the placement of the area they live in, which is known as the status bar, though it appears this is a special window placed above the menubar whose length is recalculated as necessary to accommodate regular menu items on the left and menu extras on the right. We could explore the undocumented parts of the status bar class and ways of modifying it in a haxie style but that takes a time investment that could be nullified if Apple changes the way status bars work in a future release of Mac OS X. It sounds like a fun project but I'll bet you'd probably rather we spend that time on CheckBook,
.