Be my guest! Funny thing is, after years of making prototype action figures (including Muppets, funnily enough), all with working posible joints, I'd spent a couple of days trying to think of the best way to do it on this model, and had come up with increasingly complex ways to do it- it was only on the walk down to my workshop that I came up with the almost ridiculously simple joints above!
Lesson learned: don't over think things!
That joint you used is actually totally perfect for Transformers which is what I'm remodeling. Funny how you'll spend days on something then have a simple idea show up, at least you got the idea before you did anything complicated.