Yes. Maybe we could call it: "Castellum". For example: At first buildable with "Siege Engineering". Allows: Veteran air units (airport without air transport) and Veteran ground units (works as barracks). Never goes obsolete. No culture. No defence bonus. Needs 4-5 gold support. So it would be only useful to build at the borders or later when Triumphus (barracks) goes obsolete. Your opinions?