EA, we like that you and your team get to be so creative in making things for our games. But we have creativity too.
Scenarios are interesting, but we users have been coming up with our own scenarios since TS1. Yes, Dial up internet days. I have been playing Sims for that long. We've called them challenges, and Some of them have had very long descriptions. I have printed out some of these mini novels to play with before, so I know Simmers would use a tool like this, and share their scenarios with others.
A proper tool should be able to specify how much money players start out with, and how big a sim family is. It should be able to divide said challenge into phases, with different "rules" for each section. And it should be able to limit what items you are allowed to buy. Limit what you are allowed to use, and how you are allowed to make money. Users would set a goal for each phase, anything from reaching the top of a career, finishing an aspiration or raising the next generation. And as many challenges tend to be Legacy style, the scenario would transfer to the next generation.
I've read some challenges that are build a world style, where you'd bulldoze every lot in game first, then add them back in as you finish certain goals. So a save-wide scenario would be cool to add as an option. Especially for creators who want to challenge you to play with more than one family in a town.