Perhaps buffing the torpedo launchers could work.
I propose for consideration:
- They have range and damage buff.
- Salvo size nerf (buff to effectiveness of anti-torp)
- Magazine and ammunition build requirements. magazine size and torp cost a good variable to tweak for balance. Underwater TML esque.
- reduce build time/cost (offset costs to ammunition)
Why I think this will make games more interesting:
Assuming the naval defenses are viable, they could hold off a fleet, but on a timer. Defenders get a few options, put mass in naval factories, or let the torp launchers spend mass to make more torpedoes. Maybe put some engineers on the front to assist in torpedo production speed or build more launchers.
The attacker has some options as well. Bringing in longer range bombardment, missiles or something, to try and wear down the defenses. Or rush and try to wear down the defenses. Send in a couple frigates to trick the launchers into firing, forcing the defender to toggle them on and off shoot.
The defender also gets some counter-intel options as well. Building a bunch of cheap launchers but not having them build torpedos, essentially bluffing the defenses. Attacker would have to weigh that as well.
So I guess make them viable defensively, and good, but not in a sustained engagement. might be able to catch people off guard and shred a fleet.