i agree that naval warfare could need an update, but in effect how can you do it? i mean that trick with land units is that you have so many different types that are each good for some thing or another. on the sea you have effectively just two: warships and transports.
now, one idea is to have ships able to attack coastal tiles ie land units stationed there, which is not really a totally unrealistic idea. or ... you could just go into actual warfare and see what types of ships existed in history and how they were used and see if you can come up with something. honestly, though, i don't really think an awful lot will come from this, so it will - again - end up with "the more technically advanced and / or more upgraded one will win"
for land i think the fortresses could use an update. would be cool if you could fortify your borders, build defensive tile improvements that really are a benefit, maybe zone of control or something will manage it. that might even lead to diplomacy penalty "you have been fortifying your borders with us".
civ wise, we heard a great many propositions, though honestly that's not the most important part for me. would be nice to have my country in, in some ways it would be justified, but still austria is just not quite the same category as france or america. as a leader i would in fact prefer francis josef or maria theresia, but UU would be a tough one, would know anything in particular. maybe a good cannon (the siege weapon one). as a building i would favor coffee house, but then what does it replace?
i think my vague wish is to have improvements to actual gameplay rather that a collection of scenarios. was just not what tempted me a lot.
yeah, maybe a science alliance, that you agree to research the same techs and get a nice bonus to it. or free trade area which gives you some monetary bonus, say, extra trade route for some cities (question is which ones).
the UN might even give the option that a few countries agree to build super wonders or some other thing that would benefit multiple nations. the best thing to give you an idea would be the real world ISS, ie projects that might surpass any single nations capacities but would bring enormous yields (ISS miight confer large a large bonus to science and maybe a bonus on certain spaceship parts.)
ugh, i think i will come up with some more at some later point in time.