See posts:
http://forums.civfanatics.com/showpost.php?p=10214531&postcount=120
http://forums.civfanatics.com/showpost.php?p=10213955&postcount=236
http://forums.civfanatics.com/showpost.php?p=10214119&postcount=238
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I find I never build anything other than destroyers. Cheap, fast, good damage, sees subs, and attacks planes with AA. I used to build something different now and again, but that was mainly from boredom.
Agreed. I think the solution to this is to ensure that Destroyers:
a) Aren't very good vs aircraft.
b) Are weak vs battleships (do barely any damage while getting crushed in return)
c) Don't do much damage vs infantry or better land units, or cities.
So, they're high speed and cheap, but aren't that great in combat except when attacking subs (or previous era naval units)
While Subs:
a) Are very good vs battleships/MCs and carriers
b) Are good vs destroyers iff they fire first
c) Don't interact with land units/cities
d) Are slow
Battleships/MCs:
a) Crush all surface vessels, vulnerable to subs
b) Good at shore bombardment
c) Expensive, oil-requiring.
Carriers:
a) Allow air unit transport
b) Have built-in interception capability (basically, they have some additional defensive CAG that isn't part of the air units you land on them), like an AA gun.
c) Gets crushed by subs, battleships
d) not that expensive, does not require oil.
e) No attack of their own.
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It'd be really easy if only submarines were their own combat class... for some bizzare reason the developers put subs in the standard "naval" combat class. This is why they get the Bombardment promotion to attack land units - even though they can't do so! Helicopters got their own combat class so I don't know why subs didn't as well. Who knows?
This seems like something potentially fixable?
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would people like if ships cost less maintenance than land units?
I don't really see any particular reason for this; I'd prefer naval units to be good, rather than cheap.