If I were doing it:
The way the newer plastic kits assemble I would glue the whole thing together according to the diagram and then find a good spot to cut the limb afterward for nice clean break. Trying to magnetize the odd spots where the parts normally join seems very difficult by comparison. I like the break to be about halfway between the joints on a given limb. Either midpoint between shoulder and elbow or between elbow and wrist. Its best if there some kind of sleeve or bracelet or other element that collars one section onto the next and hides the seam.
For the bloodthirster I like the gauntlet strap nearest the elbow. If you cut that and then around the gauntlet edge I think the seem would be well hidden. The wings feel a bit tricker. They probably need some kind of cavity/post arrangement to look nice. I have attached a set yet.