I saw that since ‘vkQuake’ version “1.13.1”, the crosshair is now selectable from the menu, as either cross or dot style. If I am not mistaken, the function is represented as a c-var of either “crosshair 1” or “crosshair 2”, possibly more. I think it would be more solid though if the crosshair style, was given a new c-var - such as “crosshair_style” - while the actual “crosshair” c-var, ought to be left as a traditional binary parameter, to determine if the crosshair altogether is turned on or off.
It probably would be, but maybe author of the engine decided against creating many extra console variables, or it was just easier to implement it this way. You can submit your suggestions over at https://github.com/Novum/vkQuake/issues
“crosshair n” has been a standard for more than a decade, many engines use that for different styles.
Darkplaces also has different selectable options for crosshair styles, and some of them are even different colors, and if I am not mistaken, the old Tenebrae alternate Quake engine also let you select the color of the crosshair using RGB sliders, UT '99 style.
Because of the color palette of Quake, a yellow or amber crosshair actually stands out more than red for aiming purposes.