Say you want to swap weapons or upgrade from a mk1 version to the mk2 version on multiple ships at once. It is very annoying that when you select the "[number]x <Ship>" in the Build/Upgrade Ship menu all existing equipment that the stations cannot build is automatically removed. For example in my current Save I have 20 Shih I'm attempting to upgrade at the FRF Equipment Dock/Wharf however when I select the "20x Shih" in the ship selection dropdown in the Upgrade menu, the station will remove all non-FRF equipment already installed if all ships are not identical.
As you can see in the above image when not all ships have identical equipment the game simple says "remove all non-identical equipment" and then you have to pick something new to replace things the station cannot build.
it's like taking your car to the repairshop for a small change - like getting new tires - and the shop tells you "Ok, but we do not sell 'your engine' and therefor the engine must be replaced".