I agree that it doesn't happen often but thats usually because SS's are usually the best infield defenders on the team overall and get that "captain" label. Like you said, with the constant shifting we've been doing, didn't seem like a big deal.
And I'd disagree that all OF positions are the same. CF is and has always been a different animal than the corner spots. If it can be done there, it can be done in the infield. Just gotta be selfless.