You know, Gustav sort of cannon could make a really interesting boss fights.
First, theres the whole aspect of air to surface combat, which could add some very interesting game play.
And we can have a massive mega-gun. One shot, very long reload, limited arc and very slow reaction (rotation) speed. Deals massive piercing primary damage, and a massive explosive secondary damage. Such that it can kill a Galleon in one shot. In addition, it'd have a large convoy of ground and air based units to protect it.
The player's objective would be to destroy the gun before it reached a destination (a siege of a city?). The railway gun could be slowed down by either destroying a well-defended railroad bridges (forcing the gun to take a more solid, alternate route) or damaging its engines (which would be repaired by the engineers on the railway gun). Complete kill if the player manages to destroy the well-defended bridge with the mega-gun and its convoy on it (very difficult).
Airships v. Trains!
