An obvious way to limmit bridges and tunnels would be to only allow them on costal waters, not in ocean.
Another would be to require more mentainance and construction time based on length.
Ex:
Length 1 takes 10 turns and cost 4 gpt.
Length 2 takes 30 turns and cost 10 gpt.
But as stated above, 1UPT and combat on these fields needs to be figured out.
Can a tank attack a battleship sailing under the bridge, or over the tunnel?
Can the battleship attack the tank in a tunnel?
The same goes for canals, can a tank attack a battleship sailing in a canal?
Another would be to require more mentainance and construction time based on length.
Ex:
Length 1 takes 10 turns and cost 4 gpt.
Length 2 takes 30 turns and cost 10 gpt.
But as stated above, 1UPT and combat on these fields needs to be figured out.
Can a tank attack a battleship sailing under the bridge, or over the tunnel?
Can the battleship attack the tank in a tunnel?
The same goes for canals, can a tank attack a battleship sailing in a canal?