Yeah no-kill playthroughs are pretty tough especially when you're trying to get no alerts on top of that (and on the mission that takes place on broad daylight), but when you pull it off its the best feeling ever and thats when the game truly shines.
I really want to get all the extra casettes because I listened to Paz's diary and it was fantastic and gave a lot of back story as well. I'm hoping the other casettes that can be collected are just as good.
Have you tried importing music into the game? Its a very unexpected yet hilarious feature if you set a custom song to play when your helicopter touches down.
I listened to some of those diaries, as well those dialogues that tell about the nuke situation, very cool indeed, will listen to all eventually.
I don´t know how to import music to it, and I don´t know if it is possible since the PS4 do not support MP3, Sony should fi that!