I got to build the Dreadknight for my LGS. While building it, I considered magnetizing the weapon options. Since it's not mine I didn't do it, but if you want to do it for yourself there's a couple of major difficulties. It's possible but very difficult. Seems like a lot of GW kits these days are like that.
First off there's only two gun bodies with three options. You have to magnetize all three barrels and ammo feeds which is a chore into itself. Then you have to magnetize the gun body onto the arm which is complicated as illustrated above. The servo arm locks into the gun, which in turn runs through the ammo feeds. This is not a task for beginners.
Fortunately the hands are easier. Make sure you set the magnet inside the arm before you glue it together. It includes two right hands with three options. It is possible to just magnetize the fingers on so you can use all three options. I didn't glue it in because the hex arrangement fits pretty well without a magnet.
There's a piece that I can't identify. I read through the instructions 3 times but I couldn't find where piece 75 (in the middle) goes. It's not listed in the extras like the included purity seals and Terminator Honors. It looks important. If anyone knows please let me know.
I would love to paint this thing up for the store but there's no way I could do it in a reasonable timeframe. So tonight it leaves my hands but if you have any questions about the sprues themselves I'll be glad to answer them. I might be able to get ahold of the GK squads, both the power armor and termies.