I had sourced some extra minis from an online retailer, and used a razor saw to separate the torsos and arms from the appropriate mechs. The head of the Pixie was a little harder to remove, but careful angle sawing let me remove it with the least amount of damage.
After that it was just a matter of gluing the parts into the proper spots with super glue.
I imagine pinning might be needed for the metal versions when those are released.
I did cheat on the Warhammer arm however, as I had a spare Banshee one and just crafted a shoulder using some spare panels.
I am curious how did you make it? I can see some of the different mechs used and also the original description from the source book but how'd you make it work?