Modding a useable Naval combat system?

[Haido]

Would it be so possible? After all we have the water already. Lets make some units that can "walk" upon it and battle it out.

[Oaty]

Can I hire Jesus or moses as a mercanary?

[hoom]

It looks to me like there nearly were naval battles in Rome, but they probably got delayed till the expansion for risk reduction I think.

Other people will have examined the files much more closely than I but it looks to me like naval battles would work somewhere about halfway between floating giant elephants & mobile walls ('sailing the accountansea' ~;) )
There's certainly lots of stuff in the stats that seems unlikely to be factored into the autocalc & you actually get a pre battle screen, so sticking a 'fight this battle on the battle map' button on it shouldn't be hard.