I'm hesitant to add buttons to the model panel since the button list is already kind of long, particularly for functions that aren't all that hard to access.  As a power user, you might want to consider using keyboard shortcuts, as documented here:

In particular, 'op' will bring up the open-file dialog, and 'ov' the open-volume dialog.  There are shortcuts for opening the last file you opened, the second-to-last, the last two, etc. which is convenient for quickly opening the same file(s) you were working on in a previous session when you start a new session.  Also, 'xs' will export a scene.

--Eric