Actually its very possible. Open up the mission SQM file in the mission folder.
Find the name of the units you want to change to east. Should look something like this (remember that it will be differant depending on what has been saved in the editor. Although it always keeps the same layout) :
class Groups
   {
      items=63;
      class Item0
      {
         side="GUER";Change this line
         class Vehicles
         {
            items=2;
            class Item0
            {
               position[]={3014.722412,21.959999,6051.657715};
               id=1;
               side="GUER";Change this line
               vehicle="Civilian6";
               player="PLAYER COMMANDER";
               leader=1;
               skill=0.600000;
               text="pl";
This is an example where Civilian6 (pl) has had its side changed to resistance but keep the civilian look. Possible values are West, Civ, East, Guer.
You should be able to figure the rest out (unless i botched it up).
The reason you change 2 lines is because the first line represents the side of the group and the 2nd represents the side of the lone unit.