>>5342691I've done almost exactly this to my Samus. For the shoulder I cannibalized some large joints from an old Eva-00 revoltech leaking plasticizer. I had to cut most of both posts off, and I carved the pauldrons hollow so I could attach her arms closer to her torso. To tighten the midsection I used the old glue/floor polish trick.
For the head, all you have to do is cut some rubber off the socket hole. The neck articulation is much better and the head still connects properly.
For the wrist, I cut her hand off at the panel line and drilled a tiny hole in both the arm and the hand. Then I clipped a piece of metal off a paperclip and glued one end into the hand. I then layered some glue on the other end of the rod to create a kind of mushroom peg. The hand disconnects slightly when you rotate it unless you sand down both halves to connect flat.
For the ankles I cut out some space in both halves to install a small revolver joint, and drilled the foot-side connection hole in diagonally. It's a rocker ankle, ala golden age Marvel Universe and modern Marvel Legends. Afterwards I zipped a hole in both heels to make her stand-compatible.
As for the cannon head, I don't recommend trying. That was the last thing I attempted and I fucked it up since the rubber molding made the cross-section uneven. I tried to fix that with some sanding, but it looked bad. At that point I couldn't glue the bits back together, and I still need to cast the cannon head of my spare figure to make a replacement.