I would like to point out that I served a naval gun for many years. and the argument that 'most of the gun is not in the turret' doesn't hold water.
The base of a 9 inch gun or even most 'main battle guns' was composed of the following items:
ammunition feed/ejection mechanism (irrelevant in starmade, no ammunition)
In some guns, the pilot/firer's compartment, although this was rare.
Rotation and manual targetting system. This is simplified in starmade, but is basically what is in the bottom
The hatch, servicing room, and a tunnel for someone to crawl up into the gun.
The 'gun' itself was the firing mechanism and the turret, which were solidly affixed to each other, the whole barrel/firing assembly needing to be swiveled to fire. Very similar to the new rail system.
The problem is not with rails. The problem is that shields, power, and weapons scale FAR TOO WELL. Thus necessitating big defenses and gigantic weapons. This is also the reason why armor sucks and no one wants to fly a fighter. Because big weapons are just insanely over-the top. While obviously the difference between a 4 block weapon and a 5 block weapon should be 25%, the difference between a 400 and a 500 block weapon should be far less pronounced, closer to 2.5%. and the power system needs to be COMPLETELY reworked, from scratch, eliminating the whole 'dimensionality' thing altogether.
But no one wants to call attention to the elephant in the room, because admitting it suggests a huge nerf (That won't really have any effect since everyone gets nerfed equally)
In essence, 25 turrets with 10 points of weapons each should be vastly more powerful, overall, than a single turret with 250 points of weapons. Why? because each of those turrets must also contain a bobby ai, an extremely expensive firing computer, the turret mechanism, and each of those tiny turrets run the risk of getting much more easily scraped off by a counterattack.
It's a matter of risk (and expense) versus reward.