1-2 are must haves for me, 4 not so much, nice to have but not mandatory
3 is a different topic, i would prefer if turrets scale with their hardpoint (yes dedicated harpoints with scale based modifiers for dmg, range etc., different mounting types (fixed, independent targeting) would be nice too
in short, i don´t want to have the final turrets but more of a template. A template that scales with its harpoint and one that can be used on multiple hardpoints.
Acquiring this templates from loot or turret factory (think not of manufacturing but designing a turret) would solve above points
For me it´s important to design a ship together with and for its weapon systems. So, especially early game this is very difficult without lots of resources and a dedicatet cargo ship/manufacturing station. Would be nice to be, at least, able to buy different low level guns in the starting sector for every reasonable weapon type (no energy suckers because no way to provide enough energy with iron)