Ok so, get some Daemonettes, CSM and Eldar Guardians.
The basis of the Plastic Sister is Eldar legs + Daemonette torso + SM pack/arms/gun, with GS to fix any issues. Shoulderpads and sleeves can be made from GS.
As you are going for chaos, replace SM parts with CSM alternatives and use Daemonette heads.
Berserkers - just arm them with axes and pistols. Repose into running. Use the heads with the most horns.
Noise Marines - Take any extra heads you have. Cut them in half so the mouth is removed. Now take a CSM backpack, turn the exhaust ports facign forward and GS the heads over them, so the outlet maked the new mouth.
For noisemarine guns, take 2 bolters and glue them on end to make a single long one. Then add a tank sprue gun muzzle on the end. Attach to backpack with guitar wire
Use the heads with the AWESOME HAIR
Plague Marines - This is GS work. Add huge distended bellies, pustules, and other nurgly crap on the basic chaos sisters.
1kdaughters - Either go the "headless horseman" way or make some SoB helmets. The easiest way to make said halmets is to take a Chaos Warrior helmet and GS the "panty" shape on it. Otherwise just assemble as normal.