I've done this in the past to try to get something more dynamic poses with the old XV8s.
The crisis suit on the right has fallen off of the tops of buildings multiple times but I've never had to do any repair work as I pinned all the fragile joints like the hands, elbows, knees etc.
To pin I use my normal real small drill bit (1/32" diameter I think) and drill a hole into both parts. Then I take a 1/32" diameter brass rod (Paperclips work too) cut the rod so it can fit without leaving a gap between the parts with some wire cutters. Glue the rod into one hole apply glue to the other end stick it in the other joint and let it dry. It's quite a strong joint. My drill and pin diameters don't really matter you just want the hole to be too large for your pin. My pins fit quite snug which I like but I've done it where the pin is more loose and that works too. There needs to be some room for glue otherwise you are really doing a friction fit.
The main issue is getting the hole drilled in the correct spot. You want to be accurate so the part lines up and so there is a decent amount of surface area for the mating parts to connect so you have a good joint. Measure twice and cut once because when you start your hole the drill bit will always recenter itself.
As a side note pinning works real well with weapon swaps as it can be very sturdy and you just trade out hands.