I think changing it to “stormtroopers are rising up” would be clumsy and out of place, it would take away from the whole point of the movie’s ending about how everyone needs to come together to defeat evil, not just some stormtroopers. I actually think the new Finn/Jannah lines work really well with the ending, Finn talks about how the Force brought them together to help the Resistance, and that’s exactly what happens in the end, everyone comes together to help in the fight, which brings an end to both the emerging threat on Exegol and the First Order’s reign over the galaxy.
Finn’s line and the subsequent montage do fill like a quick way to hand-wave away the First Order conflict from the previous movies, but bringing up some random stormtrooper rebellion that we never see would just add to how rushed it all is.
Yes, it’d feel like it came out of nowhere.
Now if someone could figure out a way to build up the storyline throughout the film, and have Finn send out a message to the stormtroopers during the battle, that’d be interesting. It would be ReaL interesting if someone here were working on an idea like that.