Actions that will need slow_invasion upgrade isn't limited to "Transport Disembark" and "Conquer City 2".
Move enabler upgrade to a function. Handle "Transport Disembark 2" as an enabler upgrade even if it was new in 3.1 by inserting the unupgraded enabler first.
Move punishment effect insertion to a function too.
Actions that will need slow_invasion upgrade isn't limited to "Transport Disembark" and "Conquer City 2".
Move enabler upgrade to a function. Handle "Transport Disembark 2" as an enabler upgrade even if it was new in 3.1 by inserting the unupgraded enabler first. Move punishment effect insertion to a function too.