The problem is - fleet ship management automation option will not follow that upgrade path from the get go. It will order new ships of the latest design on a shipyard but also will upgrade old ones simultaneously. Amount of ships will be increased without a reason.
The system works fine when you don't have specific designs in a fleet template (only latest for hull type or for role) and it works fine if fleet ship management is turned off. But having together specific designs in ship templates and fleet ship management leads to overproduction of ships every time the specific design is updated.
I can make a video if it's not clear for you. My English is bad, I know
