Some of the ideas sound like they could have worked, though given the Writing of the previous 3 games I don't trust it would have been anything other than action movie schlock at best. If it worked it would have been like 2, cheesy but enjoyable and with some heart, if it didn't it would have been like UC 3 and come off as a little forced.
That said, the video directly reads from Jason Schreier's book, but seems to miss that the book paints the development before her departure was much more disorganized and preliminary than this video portrays, in some respects there are hints that the initial UC4 team was very small and very much in the early stages by the time she left. So it's almost impossible to say how many of these ideas or proposals would have been changed, and how well they would have been pulled off.
It's much easier to say the story that exists mostly in our imaginations with a few points to hold it together is better than the completed work we can examine from beginning to end.
While the story ideas are different and incredibly interesting to hear about from a game development prospective, the original story ideas never got far enough to judge whether or not they would have been better than we ultimately ended up with, even the, not picking up a gun for the first half of the game, idea sounds horrendous at first, but was likely proposed early enough in development that they were exploring ways to make the climbing and sneaking more engaging so never really existed past the proposal stage.