Well there could be a game mode that is entirely dependent on coastal territories. Lets call it "Beach Head". In this case, fleets are the main base, and send "amphibious assaults by your army design to establish a Beach Head.
This could be doable in terms of Balance because
EoN lets your swap builds for next re-spawn. So, lets describe how this would work with the said mode:
Game Mode - Beach Head
Coastal territories can be the next staging ground when invading continental bodies. After you've gained access to the coast, a land battle ensues for the coastal water front, in order to gain access further inland or simply secure the coast to prevent any flanking on a territorial matter.
You're starting locations are your fleets. From them, you spawned your land army builds. With use of amphibious and air units, you attempt to establish a beach head for a forward base by capturing all points along the Beach Head and hold them for a desired amount of time.
In turn, your ships will provide fire support from a distance, and the enemy will have fire support from inland via NPC assisted "bases" to give them a sense of occupation as well as some balance.
The balances of this would have to be pretty carefully tuned. Since unit caps seem pretty small on this game, amphibious carriers and transports will take up space that would've otherwise been filled with dedicated fire power.
Also, I wouldn't think your fleet would be able to fire to far inland. They would be meant to balance your lack of numbers due to transports taking up slots, but nothing more; while the enemy's entrenchments via far off artillery and whatever else is meant for putting on the pressure as soon as you start gaining momentum on the Beach Head itself.
Now I'm only offering a "game mode" here because the development team hasn't given us a lot of info of what happens when you capture territories. Most maps seemed very mirrored in design so... I don't know what their agenda is.
For instance it'd be totally baller to have the ability to donate cash to build actually "pre-made" defenses on that Territory. Or to build "Air Fields" or "Silos" on others. Thus adjacent battles get new "call downs" and have a map already partially defended by allied NPCs. But this really starts messing with balance issues here and have a faction controlled by thousands of players trying to make a decision uniformly would be hell. Some one would have to be elected king or something, you know what I mean?