I would say your best bet would be to save an array in game mode or game state of references to all characters to be affected, then when you change a value, say bIsBlocking, you access the array, loop through and flip their bools accordingly. If you wanted to avoid using framework classes, you could make a base character class that all relevant characters would derive from that contains the array mentioned above (static would be best but not essential if it’s not a big game).
If you wanted classes other than characters to respond, you could either make a base actor class or make an interface.