ehh...so different kit, but same weapon that needs a different crosshair? Maybe make 5 different versions of each weapon? Thats the only thing I can think of...but I'm not at home.
in interstate you choose the colour of your glasses.. so in the same way you could have the glasses model actually be a crosshair model in front the players face.. if only viewable from the players perspective.. and 'close' enough to the player then nobody else would see it..? that could work.