carolinesimsisms There aren't many, or perhaps any, modders on this site who could help with this. I'd suggest asking on Mod the Sims or the NRaas site. Or you could join the Lazy Duchess Discord server, where conversations are hit or miss but can get very in-depth.
If you want to look at an existing example of a retuned version of EA story progression, Simler90's mod includes that. It's a core mod and so is far-reaching, and this is not me recommending it for general use; I'm just saying the example might be useful, all the more so if the author has provided the source code on GitHub or similar.
