I'm not too excited about the way sea travel is typically done.
I really don't like cities building harbors and then building boats and then having to load troops onto boats.
I also don't like units turning into boats to cross the water. There has to be a better way.
I have spent many hours pondering this conundrum, and feel that the most elegant solution for FE is the introduction of four new traits, with additional specifics outlined below. The first two are Water-Walking and Transport, both available in three levels. The different levels of Water-Walking determine what types of water tiles the unit may travel on; and those of Transport indicate how many other units may be in the army for that unit's movement traits to over-ride the other troops' (respective to army sizes). The third trait is Aquatic, a weakness restricting mobility to water; and the fourth could be Land-locked, limiting access to the seas. These traits may be inherited by a variety of unit types, and in many different ways.
Beach tiles acting as gateways through the cliff wall that separates sea from land, and which may be researched, controlled, and constructed upon (and perhaps created), are additional ideas. Rivers could also be made accessible to certain classes of Water-Walkers and Transporters, enabling interaction with river-side tiles while "in transport".
Water-roads is another great idea by Heavenfall, which need not be mutually exclusive.
A. Flying shows us that the only thing necessary for Water-Walking to be interesting is stuff to do on the water.
B. Four new traits
B.1. Water-Walking: available in three levels, each subsequently granting access to rougher water tiles.
B.2. Transport: over-rides all movement capabilities of the other troops in the army, also available in three levels, each subsequently allowing larger armies to be affected.
B.3. Aquatic: a weakness restricting mobility to water.
B.4. Land-locked: a weakness restricting mobility to land.
C. Spells / Units / Creatures / Vehicles / Mounts / Items with some or all of the above traits.
D. The raise (and consequently lower) land spells could have their mana costs reduced to 5 or 10 (more terraforming = more fun anyways, especially with the beautiful updates on the cloth map).
E. Only armies with a Water-Walking unit that has the appropriate Transport trait for the amount of troops in said army could access waterways. The 3dimensional model for this unit would be used to represent the containing army, and it's movement points could supersede those of the other troops.
F. Beach tiles could act as gateways through the cliff wall that separates land and water.
F.1. Beach tiles could be limited to only functionally granting passage once brought under a player's ZOC, researched, and developed (higher level structures imparting larger modes of transit, and allowing for bigger armies).
F.2. Upon completed construction, a unit could be produced with some of the traits listed above, similar to the elementals created by shard shrines for Binders.
F.3. Beach tiles could be connected via a similar system as roads. *credit to Heavenfall for this idea
G. The lower land spell could be adjusted accordingly to change cliffs into beaches (which would still need to be brought under a player's ZOC, researched, and developed to be of any use).
H. Water could be further categorized into different types of tiles with varying effects, such as shallow, deep, calm, and stormy (perhaps even limiting certain size armies/transports to certain areas/depths, or influencing the route generation for "sea roads").
I. Rivers could additionally be classified as water, allowing for interaction with directly adjacent objects via aquatic routes (the limitation of using the afore-mentioned beach tiles in order to actually move on or off land still standing).
J. Units on water could require additional upkeep.
K. Any combination of the above at all.
Additionally, the beautiful cloth map and lore behind the game are practically screaming for enhanced terraform features, simply by making them more prominent; even through subtle changes such as increasing the availability of the raise and lower land spells (by reducing their cost and/or giving them to all Sovs for example). This would also have the effect of turning the water into a playground for earth channelers (and potentially water, or even all other channelers as well). The skies are already dominated by air entities. We can wait for an expansion to discuss tunneling for fire.
Again, all that we really need is stuff to actually do on the water.
Thank you for reading.