Well, I was looking for offensive stuff moreso, but really I enjoy all football strategy discussions so I definitely enjoyed the read. I've read and applied a lot of what you wrote already. In Madden terms, oen way to apply the play switch is let people do all their hot routes, then switch your D.
I'm pretty well versed on the defensive strategy side of these formations, shown by my bullet points talking about weaknesses.
I just wasn't sure why certain teams put players in certain places beyond the very basics, which I tried to list. I wasn't sure if there was some method to the madness that I was never aware of. Judging by the responses, I pretty much was on the ball with those ideas.
I think if anything mixing up formations is just a way to create favorable matchups for your offense. Also, I think a lot of people adjust a certain way to a formation regardless of the previous plays called, and it's good to pick up on that. For example, many people seem to call man blitz against bigger personnel formations in order to stuff the run. With that knowledge you can adjust accordingly.
Think of formations putting blockers overloaded on one side to "out-flank" the defense. I guess it could apply to passing sets also.. especially when users "show blitz" at bad times. I've thrown numerous TD's on 5 yard outs to slot WR Mike Wallace because someone tried running a man blitz and hoped the safety could cover Wallace. Big mismatch.