I tried to upgrade my peasant to use a different weapon.  After I finished I tried to save it and was given the dialog to give him a name.  Since this is an upgrade it should at least default to the same name in my opinion but the name was something new.  I tried entering the same name (Peasant) but after completing the peasant was not using the new configuration.  I tried again and this time gave it a different name (the default Basic Knight or something) and the new unit was still not created.  I needed to design a whole new unit instead of using the upgrade option.