Exploitable Refit Times:
Description: By creating a pair of refits, you can reduce the time and cost of an effective refit of a ship.
Action Taken: I intend to refit an older design, say an "Idaho" class BB. I create an updated refit the usual way, and save it as eg. "Idaho (1910) - 2". There is an associated cost and refit time reflective of the changes made. Then immediately refit the "Idaho (1910) - 2", make a trivial change, and save it as "Idaho (1910) - 3". This will be a much smaller cost and refit time because it is a minor change relative to the (2) refit. I then refit two of my base model ships, one to the (2) refit and one to the (3) refit.
Expected Result: Both refits should take about the same cost and time, since they reflect very similar changes to the base design.
Observed Result: The (2) refit is significantly more expensive and takes much longer than the (3) refit. eg: 4 months versus 1 month, and $20M instead of $5M.
Credit: My buddy SherpaTheYeti
(He says, "Amazing game by the way - big fan")
PS: I realize that doing the refit cost calculation on the fly probably involves loading the ship designer, which is impractical. But perhaps you can calculate & store the upgrade cost relative to every older design and apply those numbers at refit time?