It would be possible in certain ways, but it would to be a custom window that was called _inventory at the end, such as some of the mods out there that display the ammo slot, ie: eq2ui_mainhud_inventory.xml
And to display only the number, you'd basically be able to do it only by making a page, and puttin the icon, but move it so that it only display the bottom right hand corner of the icon.
That's the only way I can think of doing it, and that limits you to where you can put it...
