I think twitch has stream delay. Turning that on would help with stream sniping. Won't do anything with the other side learning your sides strategy in scenarios though. And I don't know how long you can delay a stream. Probably won't help too much on a 45minute mission.
But imo half the fun of scenarios and fso is the strategies. Making a plan, seeing what the enemy does, analysing what worked and what didn't, then adjusting. That rush when everything comes together perfectly and that humbling moment when you get completely picked apart. Then you dust yourself off and go back to the drawing board. Stream sniping takes the fun out of it for both sides. So just don't do it (the sniping, not the streaming).
I'm all for anything that gets this game more exposure.