Unless Ren'Py is some weird monstrosity of coding, which I know it's not, then this taking a lot of time makes no sense. Each character would pull from a database of things to say, all it would take is proper tagging of dialogue based on the events you've seen, creating an icon to indicate that a character has new dialogue, and then using a simple series if "if "x event has happened do this dialogue and this icon on this character", if else "do not." It's not quite as simple as that, but it's not something that should cause a major delay. A programmer worth their salt could whip something like this together for the small number of characters, events, and dialogues in the game within a day. If the programmer working on this game can't do that without much trouble then they should be fired due to incompetence and if they can't find the time for it they should be replaced.