Here's something that might be a reasonable addition at some stage; modular multi-mission ships. I noticed there was a suggestion mentioning modularity with regards to shipbuilding (ie, speeding up build rates by using several slipways on one ship), but what I mean with this is ability to design and swap out mission modules (along the lines of the USN's LCS concept, if anyone is familiar with it).
As to how this would be implemented, while I do not know how the game handles ship components at the moment, the basic idea would be to allow the player to design a 'Mission Module' section through the Design window, and then equipment modules for it some other way. These modules would just be normal components packaged togeather which could then be 'loaded' into a Mission Module, and would probably built using construction factories like components can be now.
Now, obviously flexibility comes at a price, and this should be in the form of extra space needed for the systems to interface. So for example, lets say I'm building a 6000ton cruiser and stick a '1000ton Mission Module' I've designed onto it. This module could then load a predesigned component 'package' up to say 700tons. This would allow me, for example, to swap out the Active Sensor and FCS depending on the missile loadout I want to assign.
These could be upgraded through research, and potential areas that might be improved are;
-Efficiency of the Mission modules (How many % of the module can be used for 'packages')
-Total fraction of a ship that can be made up of modules (Initially 20-25%? Could be almost the whole ship eventually, allow for extreme flexbility - this would be the total ALL the modules make up, if multiple modules are allowed, or else you could just restrict modules to one per ship)
-Time required to swap out modules (Should increase with module size, so a 500t sensor package swap will be much faster than a 2500ton weapons reconfiguration)
-Possibily internal armour on the module itself?
The advantages of sacrificing some tonnage for flexibility would include;
-Ability to design and repurpose ships to fill a variety of roles. This could go as far as for example having a 6000ton cruiser which mounts a 2500ton combine weapons/sensor package that allow it to switch between cruiser and escort cruiser roles (in this example, the magazine and engines would be part of the main hull, the module would feature your choice of FCS, Active Sensors and Launchers). This could also work for commercial and support ships - being able to swap out cargo hold modules for a troop transport module, though this would obviously take a lot longer than similar military swaps due to the size of components. Eventually this system could even let you swap out entire propulsion packages, allowing you to tailor your fleet to whatever role its playing at the moment (system defence? trade for more speed with less fuel and engineering spaces).
-Capability to extend the lifetime of early ships without refits, or in conjuction with them. Those 1500ton frigate that you built early on could have their 500ton mission module (able to hold say 250tons) refitted with a newer version able to hold 350tons. This coupled with the ability to swap in a 'modern' mission module means these ships would have longer lifetimes (if this is a good thing or not depends on personal preference!).
-One further possible use of this would be if a ship with such a system took damage to its 'mission package', but not the module itself. Such a ship could then simply swap out the damaged module for a new one while the old one if repaired. I dont know if thats within the scope of the game though, or if it would make thing too complicated.
Obviously there would have to be some logic to make sure this fits within the existing ship design paradigm, such as ensuring either the ship has enough crew to cover the modules needs, else prevent it from being loaded? Or require modules to have self contained crew quarters. Theres also potential for conflict between the Military/Commercial categories, but I suppose this would be solved by restricting Commerical modules to only loading Commerical packages. Mission module would probably only be able to take one package a piece, up to the maximum 'capacity' in size wise - so fitting an undersized module would be possible, though wasteful.
Hopefully that made some sense. I have no idea if it fits your vision for the game, but it was something that occurred to me as I was learning the game.
Elouda