If you are talking EAW or OP, then using ShipEdit is a great way to add ships. It's easier to do if you edit an existing ship (find the closest thing to a Sovereign and change it around with ShipEdit). You can't add any new weapons, unfortunately, but you can do almost everything else to make the ships. There are some mods that change the weapons names through the strings.txt file but the stats remain the same -- so a hellbore can be changed to a Quantum Torpedo, but it will behave exactly the same.
I'm not sure about the year scripting. You might be able to change the eras with strings.txt too. However, you can definitely change the dates the ships come out just with the shiplist, which will be easier if you only have a few ships to swap in. Good luck!