@hayhor from what I know it is not that hard if we talk editing cfg files, you just need to know command list (aka what each line actually does in game).
Yet it is clear there is a veeery limited info on that in Apex and also part of the stuff as far as I understand is forced onto client machine by a server - you can change stuff locally yet it will not work.
Crazy how above said is true yet you still have cases where people can make such a huge change as crosshair. Reminds me of that video where a person changed game's graphics via nvidia panel and lodbias setting change <- known parameter of the Apex base engine.
Anyway thanks for the info, if someone knows how to manipulate cfg files post here or PM, I would gladly take a look at other crosshair options :P