I would like to suggest a hybrid ADS mode wherein we can use both the Toggle and Hold option when using ADS. I found this on a certain game that I won't name but it's incredibly helpful on certain situations. I mainly use Toggle since it's more light on my arms, especially if I need to drag my mouse a full 180 degrees to turn around while aimed down, or just rapid flick shooting for general play. However, I found out that the Hold option has its perks. Like quick scoping (effective especially for the Witness encounter), or swapping to your shotgun in PVP while holding the ADS button (pulls out your shotgun directly into ADS), certainly not possible on Toggle since the shotgun needs to be fully drawn before you can aim it down.