Isn't this the plot of the first Cloverfield movie?

I've run two successful one shots with different degrees of success. The first I completely improvised, no notes or anything, and the ending did feel a bit rushed but we wrapped it up in one session. The second I ran with just one major theme in mind and the rest was improvisation. It helped that I set them up in-universe with the main campaign so the end goal was just to create consequences for the main party, good or bad.

I love the Mass Effect series! (Only played the remaster) but I loved the way my choices had consequences throughout the trilogy. Like the dialogue trees were really fleshed out for their time, I'd even argue for modern day.