You would need oxygen and nitrogen anyway. You could use hot nitrogen (heated resistively or as plasma), you don't need acetylene.

Humans need room–temperature nitrogen, not nitrogen plasma. You would rapidly make the atmosphere inside your bubble unlivable. There are few easy solutions here.

Then you wait a moment until it cools down. Of course there are few easy solutions, space is very hard environment mercilessly waiting for you to make an error. You can find problems in every step. It doesn't mean you should give up before you start.