I didn't quite understand. In the final version, does your city's recruitment window only display one third-tier creature?
Here's the thing:
You can make it so that Royal Archers are displayed in the second slot (by setting a different sequence in Upgrades), but then you won't be able to upgrade Archers into Marksmen, or Marksmen into Archers.
Or, you can do it the way I did, and then you can upgrade Archers into Marksmen and Royal Archers. And Marksmen into Archers and Snipers.