I am aware of the Uniform issue that they disappear when you start the mission through the Secnarios sector , this is unfortunatly an Arma issue and haven't been able to find a way to actualy fix this.

The counter this the best option is to :
In the mean time im trying to get Bohemia's attention to fix this , if you can please vote : http://feedback.arma3.com/view.php?id=26674