I don't think the map matters too much as it is just about a plain mindset: What counters what?
In theory, long range could work on small maps too, it would just be harder to maintain range and gun arcs.
However, one could also include the very maps where this or that counter fails to counter against this or that ship/build.
Ship stacking really limits your team's flexibility what with 2 ships having the same advantages and disadvantages.
Regarding the Mobula and mine thing, because the Gat/Carro Pyra is as strong as it is and not rare at all, I thought about trying to counter specifically this build with a Mobula. That involves lesmok Gatling, because they will get too close for hades anyway, double artemis and a top top, middle top Mine Launcher. It's sillyness has yet to be tested, though.
I usually don't trust mines to hit, so I want to avoid using them on pretty much every ship I have, with a few exceptions.
Junkers have a general problem when dealing with flechette damage. I heard it isn't so bad once it brings 2 or 3 carronades, which sounds almost as bad as double heavy Carronade Galleon side ("They are destroying your balloon? Destroy their balloon more!").
The ship combination of Metamidion and Blenderfish is a pretty solid one. They can close distance rather quickly, disable a ship and focus fire the not disabled ship. Is that one un-counterable, are mines the only possible solution or is there a less silly counter?