Would you want shadowborn FOV to be a toggle option?

If one could properly operate with a 360 FOV, yes, it would be a benefit over 87, but I do not think that performance would be significantly impacted at all due to FOV bearing little say on chases. Personally, I would argue against this as I do not think a survivor should be spotted by a killer who is looking into the complete opposite direction, that would just feel annoying and unfair to the survivor. Now, I think that the objective conclusion is that a good killer is good regardless of FOV and a bad killer is bad regardless of FOV. Still, 360 degrees would be rather silly, probably even more sickening than the current narrow 87 degrees, would be superfluous and thus unneeded and unjustifiable despite likely not inflicting any major hinderances to game balance.

Values such as 270 and 180 will be the same, I do not see them causing any major issues but also do not see why they would be needed. The added information to the killer might make it harder to approach or walk by unseen as a survivor and might reduce the time you have to hide when the killer is looking around, but in those situations the killer can already achieve the same effect by moving the camera quickly. Stealth would be a bit harder but not impossible by any means even with those values.

Now, why are +15 degrees okay but +150 are not? I think that would depend on what you believe defines "okay". If the answer is balance then I would say anything is objectively "okay". However, overbearing value such as 360 might feel unfair and unfun to the other party independently of its actual weight on balance. So, when we take player experience into account we can see why extreme values would be discarded while those in-between would not.

And I disagree, a few degrees is not only accessibility, it is both accessibility and an advantage, it is simply not all that great of an advantage nor one that adversely affects the game. It is known that narrow fields of view may cause motion sickness or discomfort, so can wide ones. Thus, ideally we would have a slider where the player is allowed to adjust in between a lower value that is sufficiently narrow and an upper value that is sufficiently wide while also not causing the other side to feel cheated.

Since we already have a narrow value in the current FOV, the discussion turns to the upper limit. I would argue that the 102 of Shadowborn is a nice compromise as it seems to help people who have issues with the base FOV while also not being high enough to cause a sentiment of injustice by those caught within its cone even when one is used to playing against the narrow 87 degrees FOV. If you disagree, I will be glad to hear why.

In which games, core gameplay is based around field of view? Name me few please.

I don't recall any game that "what can You see" is part of game premise, and fov slider is available.

And you still refuse to accept shadowborn exists. That is on you

I believe the opposite. Icons was necessairy, but i think its was terrible change. I would rather see old dark maps, with no swfs allowed, with no icons. I bought the game because it was a horror game back then. Now its more like playground of some sort.

Also

"damn, I would have won if it wasn't for that pesky Shadowborn!"

There was a time when i thought "dam, i would have won if i dont always list track of someone going my right". Then i used shadowborn, and its my core perk on Wraith and Nurse. Sometimes other killers, and will be on Blight and Legion. It really helps to see what is happening around me, and gives survivors less opportunities to run away from me, its basically "hold W" with little exceptions.

Fov slider would really helps me as killer, and would really screw my game as surv. Its good its locked on perk.

Are you sure, that those games are based on non-seeing enemy? and any bit of fov changes strategies? I agree it may be easier to track enemies, but i really cannot see any changes in stratgies in terms of increased/decreased filed of view, where in dbd its essential to control how much people see. And its not only fov:

Nurse is loosing not only some fov but also is loosing control over camera while she is in fatigue. Should this slider also allow her to see more in this stance?

Trickster have part of his fov covered with light when his main event is ready.

When braking the paletes of vaulting, killers loose control over camera to limit their perspective - its also a part of gameplay, the same as fov - to control what killer can see and allow survs to have some advantage and technics. Should we remove those cameras angles due to accessibility?

where is the line? why there?

and last, but not least - fov also affect at which angle killer can be blinded and stunned by flashlights.