They've confirmed that fires, passengers, and other "mission-oriented" items will only be in the mission structure.
So the downside is that you'll have to get your ratings when you first get FS2024 to unlock the firefighter pilot missions. I don't mind this, as (1) the missions sound fun, and (2) you can apparently go straight to the rating tests without doing any training missions if you already feel confident. You'd need Private, Commercial, High Performance, Turboprop, and Scoop ratings to do firefighting. But once you've done those, the sky's the limit.