The latest feature I have been working on is the ship refitting and replacement system.
Only the ship roles can be specified when creating squadrons or configuring fighter/mining/salvage command facilities.
When a ship is built, it will automatically be sent to the correct assignment (corresponding to its role) If the ship is not needed then it will be stockpiled in the reserves.
Each role can contain any number of designs, but the latest designs will be prioritized for replacements.
Ships with obsolete designs will be sent back to the reserves if there are enough newer replacements.