I'd also suggest pinning it, but with a small difference: use multiple pins.
Specifically, I'd either drill a hole big enough for two pins or two small holes. Then using either brass wire or brass wire and some wrapped guitar wire, pin the parts back together.
The double pin will add some of the lost detail back (especially if you use some wrapped guitar wire), and stop the parts swivelling around too.
The pinned assembly will be much stronger this way too.
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If you prefer though there's another alternative again: you can simply clip the maniples off at the "cuff" and the shoulder, and replace the whole lot with wrapped guitar wire arms.
This would be the simplest and strongest method of all, give you something cool-looking and retro to paint, and also allow you to pose the arms however you want.
In either instance, I agree that this model and Hoffman's armature are very stupid designs from a practical sense, especially given that a lot of Wyrd's metals are not the best castings.