Why not drop the tradition and go the other way completely?
Make the "national wonders" upgrades (replaces) to normal building (monument, barracks or mil academy, library) that costs just a bit more in upkeep with the same base output and a bonus output depending on the number of other libraries etc in your empire.
This way you can build it early and as your empire grows so does the usefulness of the nw.
Make the "national wonders" upgrades (replaces) to normal building (monument, barracks or mil academy, library) that costs just a bit more in upkeep with the same base output and a bonus output depending on the number of other libraries etc in your empire.
This way you can build it early and as your empire grows so does the usefulness of the nw.