1) Go to your profile folder which is located under 'My Documents\Shadow Warrior DX11\profiles'.
2) Open binds.cfg with Notepad.
3) Add the following line first. Note that adding this line will bind what may be called 'HUD Off' mode to F11, with a FOV value of 100; so feel free to change the key and FOV to your liking.

bind +f11 "r_draw_hud 0; r_draw_weapon 0; r_fov 100"

4) Add the following line right after. As with the other one, this line will bind 'HUD On' mode to F10, with a FOV value of 80; so change the key to what suits you best and FOV to what you use normally.

bind +f10 "r_draw_hud 1; r_draw_weapon 1; r_fov 80"

5) Save and exit.
You can now use the binded keys of your choice to toggle the HUD and the first-person weapon models on and off during the game, as well as going back and forth between the two different FOV values while doing so.
Here is the result with the above-mentioned values (which I personally use):