Create the player unit as East. Create a west unit. Group the two so that the west unit leads the group. Write this setCaptive true in the in init field of the player unit. He will be side west since he has a west leader.
At the start of the mission deletevehicle the west soldier. (Can you do this in init.sqs?)
You can now walk into the Soviet base, dressed as a Soviet officer. They won't shoot at you because you are setcaptive true. When you are detected, or blow something up or whatever, use a trigger to make you setcaptive false so that you will be shot at.