When you increase/decrease your FOV and zoom in with a scoped weapon the scope itself will occupy a smaller segment of the screen, making the zoom less effective as well as making the markings on the scope less legible, accurate and useful (see attachments).
The zoom levels and scope sizes should remain consistent regardless of FOV settings. {F25828}
This brings unfair advantages and disadvantages in different situations. It is extremely unfair in PVP where there is no standardization between all players.
FOV affects both picture from eyes and optics. It is quite understandable.
One who thinks want to see more but less detail set 90 degree FOV. And in same way it will affect his optics.
Second one who thinks he has small monitor and dislike "view flatness" sets 60 FOV. He sees less but more detail. In same way it applies to optics.
Separation of these FOVs could be solution.
Official BI stance is already supporting my report, see here: http://feedback.arma3.com/view.php?id=6780#c25983
Adjusting FOV can only be done by the use of mods. Sorry but this is not a bug.
Thank you for your report.
Adam
It was brought to my attention that FOV can be changed WITHOUT the use of mods - via a change in the player's user config file by adjusting fovTop and fovLeft values.
This is an issue because where servers can whitelist specific mods, they can't enforce changes that are done in the user config settings.