A feature that increases the number of unique interactions the player and the villager can have. This could also allow for “action” interactions to appear more often (the villager wants to visit, sell, buy, change catchphrase, write a letter, adopt a design, etc.)
These features normally occur when the villagers have developed a strong friendship with the player, but they take a long time to be triggered and are not as recurrent. Having the possibility of a more dynamic gameplay would do wonders for replayability and having more stuff to actually do besides catching bugs and fishing.