There is a lot of posts about various systems and how they work and which ones have caps. They also probably do a lot better job of explaining them than I could as well. Goggle "starmade wiki" and you can dig out quite a bit of information.
Some aspects of large capital ship design.
Ship overall dimensions. The longer a ship is in a particular dimension the longer it will take to turn. Really long ships like the one your suggesting will take a very long time to turn left or right or up or down. You will be able to roll fairly fast though. For maximum turn speed in all directions be borg and be a cube but that's usually not so good looking unless your good at varied asymmetrical surfacing. You will want a jump drive.
Power is pretty simple a few long lines till you hit around 1mil e/sec then make a duplicate set as a backup after that its all just blocks of power reactors as you have hit the regen limit and its limited to 25 per block unless you use docked entities.
Multiple docked rail entities some types of which are
Modular power cores
Something to look into now that they have changed to output per block its now viable option for large ships.
Increases the power to mass ratio if setup right requires logic and power supply beam and a lot of fiddling.
Turret systems also point defence turrets
Fixed weapon systems AI controlled
All these docked entities have advantages with energy storage and power generation since they are separate but can draw power from entities further up the chain back to the main ship hull.
With the new rail system there are a lot of combinations now possible than the old docking system.
Also the shield systems also protect docked entities a bit read up on it.
Moving about in your large ship 400 meters is quite a long walk let alone 2.6km.
Including railed platforms and logic to move them. Its slow but you can hop on and do something else while you wait.
Gravity tubes to move really fast around the ship. But only if one person is running around. Multiple people confuse it as you can't use a lot of the logic modules to control gravity. Generally limited to basic on and off by area, floor trigger or activation block.
Automated hanger doors.
External controls for doors.
Faction permission if you want non faction members to dock or access.
A control room indicators for hanger doors or docked ships maybe some way of viewing them. Otherwise its a long walk to find a hanger bay empty.
Get your small ships done first since they decide how big the hanger needs to be at least. Include wireless logic module so later you can link and control a specific hanger door.
Your going to need good turrets since almost anyone can get behind you.
Weapon systems applies for all ships.
This requires a bit of research in what you want to do and how to effectively go about it.
For example:
The toughest armour block is 1000EHP with piercing defence maxed out its 2500EHP so any cannon or beam that is explosive that does more than 15000damage is wasting damage. Explosive effect is to spread the damage out to the hit block and the 5 connected blocks with a 1/6th of the total damage each. But a system block might have only 50HP so at that point anything over 300damage for an explosive cannon or beam is a waste.
To destroy a planet unless its changed its 10mil HP core. A missile is good for this as long as you have enough energy to fire it and its radius is enough to go through the planet segment and hit the core. If there is point defence a good large long range piercing weapon. If shielded piercing won't work.
Power batteries should be one continuous block to maximise power storage.
Large salvage arrays can be setup to reduce lag by mining a block per hit rather than multiple hits required per block.
Keep in mind in future there might be capital systems added to game which may allow the functionality of some starbase systems for some penalty. For instance manufacturing, Warp gate. Or a hyperdrive.
Research
all weapon slaves for all weapon systems. You can skip pulse its far to short ranged for a capital ship but might be good for clearing some room around you if your bumping.
weapon effects punch, pierce, ion, explosive, overdrive the others are useful as well in certain situations
defensive effects pierce, ion the others as well.
Hope this helps.
