Isonzo moderators on Steam forums told me that i was asking for innaccurate and immersion breaking stuff for the game, that is absolutely false. Beretta M1918 was in the game files since beggining and its now finally implemented in the game along with cosmetics such as Dunand visor and various painted stalhelms and very cool uniforms. This is how you perfectly balance between accuracy and creative liberty, Isonzo is now on par with Battlefield 1.
https://www.youtube.com/watch?v=PRJNOd8hCgk