I think that earlier ships i.e. pre-firearms tech
may or not have ranged capability depending on various factors such as size.
If the theoretical background - which I share - is them to have or not archery units, then it is logical that the ship in argument
should host them to have this benefit.
I'm not sure if this was the case in history, but I suppose that it should be possibile to host a certain number of archers on a bireme too.
I'm pretty sure ancient sailships were used to carry troops to overseas targeted lands.
I think a bit of research is needed to say how many men any type of ship could carry beside the crew needed to operate the ship.
Then, we can suppose in CIV universe at least a portion of this value is used to carry archers with their number and abilities depending on ship type/size, techs, promotions and so on.
I would suggest to add a tech that both enables and regulates the matter, for the sequent advantages:
- preventing spamming of ship ranged attacks in early game by all civs.
(thus leaving intact original naval combat in such phase, avoiding unbalance and repetitivity)
- add more depth to warfare research
(you can choose if you want to specialize like that or not)
- have a solid system to regulate this delicate and promising feature.
We could in fact have a tech that has these effects - also side ones to balance (see 2nd point above)
- enables naval ranged attacks (in any age, but changing with techs)
- sacrify a portion of your cargo space to host ranged units (e.g. archers with archery)
The second effect will be negated by gunpowder thus allowing modern ships to have ranged attacks but with firearms w/out sacrifice of any cargo space.
Each achievement in the research line that involves tech related to navy, weapons and such could allow for the creation of new units/promotion older ones.
The same with successful combat that give new xp to units.
So if you start with plane archers you would then achieve such things as progressively increased range, fire arrows (ideal vs sailships) and so on.
I would not leave this exciting feature only for naval vs land units combat.
I would add it to naval combat too, thus allowing a more thrilling game and more depth.
A ship with ranged unit capability would have a big advantage vs a basic one of the same type, IF you manage to use this properly in tactical map (ie stay at a distance)
Those are advanced features however that could be done in future releases, btw.
Let me know what do you think about.
Good work as always.