Here are my "up armed" Servitors to go with my Enginseer, which is a Forge World Myrmidion. The changes are pretty obvious on the servitors. I added some more fairing/power plants and servo arms from the old Fabius Bile kit. Those additional bits hide the magnets to swap out the servo arms for Heavy Bolters or Plasma Cannon. These were actually done some time ago, to be deployed in my club's Burning Stars campaign and Apocalypse game. I'm lazy with updates sometimes.
The Enginseer has re positioned power axe arms that have a magnet mount and pin to make storage way easier and the pose more dramatic and crowd friendly.