For now, it's possible to use the models as helmet; on future updates I'll prepare them as new look model and share.

You need Scripthook and Scripthook.net to work!

GTA V Basic Tutorial Convert Weapon Mod - How to Edit ydr files
https://www.youtube.com/watch?v=G552Euni-6k

Installation:
- Copy "MaskAlwaysOn.cs" file into Grand Theft Auto V\Scripts file.

- Choose the model you want to add to the game.

- Start OpenIV

- Navigate to: Grand Theft Auto V\x64c.rpf\levels\gta5\props\lev_des\v_minigame.rpf\

- Enable Edit Mode

- Copy prop_welding_mask_01 file into v_minigame.rpf.

- Copy accs_diff_011_a_uni.ytd, feet_diff_015_a_uni.ytd, lowr_diff_024_a_uni.ytd and uppr_diff_031_a_uni.ytd files into
64v.rpf/models/cdimages/streamedpeds_players.rpf/player_two.

- Press NUM PAD 7 button during the game in order to activate the mod.

- For Billy The Puppet character costume, go to High-End Clothes Store and buy the Tuxedo among the clothes at the right.

Special thanks to Proudnoob4, f0rest and Pandassaurus for the script.

*For some textures I benefited from Saw: The Video Game