Danse insists on wearing his power armor at all times, but once the ArcJet mission is over, he never puts his helmet back on, even in the heat of battle.  This makes no sense. Turns out, once he's your companion, he doesn't even have a helmet to put on! I mean, come on, I admit that Danse can be kinda dense, but he's not that stupid.

This is just a pair of batch files to create and then set up a helmet. It had to be split into two batch files, because the game has to run briefly in the middle, and I don't know any way to do that inside of a single batch file.

You ask, "Why not just find a BOS II T-60 Helmet and give it to him?" That's because he wears BOS V T-60d power armor, which you won't have access to.  These scripts produce a BOS V T-60d Helmet, which is exactly in keeping with his other armor pieces, so this process should qualify as lore-friendly.

Installation:
    Unzip to your "Fallout 4" installation folder.  If you don't know where that is, then hm, I'm not sure you should be doing this.

Alternative installation:
    Unzip somewhere else and copy "makeHelmetForDanse.txt" and "makeHelmetForDanse2.txt" into your "Fallout 4\Data" folder.

Usage:
    - Run the game
    - Go find Danse and make him your companion
    - Open the debug console
    - Type this and hit Enter: bat makeHelmetForDanse
    - Exit the debug console
    - Let the helmet drop to the ground
    - Open the debug console again
    - Type this and hit Enter: bat makeHelmetForDanse2
    - Exit the debug console
    - Tell Danse to pick up the helmet
    - Open Danse's inventory and equip the helmet for him

That's it. Ad Victoriam!