Including all the main realism mods is important, as done in other games. They would be toggleable, of course.
I've just imagined 3 of them:
The first one would be the notorious:
No-Real [NR]
The second one would be the popular and the most used:
Traditional-Real [TR] (CKR 1.1)
and the third one would be a very real one:
Ultra-Real [UR] or Hardcore
- no crosshair, breath while aiming, worse aiming after having some gun-shot on arms, hopping when get it on the legs...etc...thinking and also waiting for further ideas