I’m not sure I agree with all of your ‘rules’ for photographig twins (different heights, diagonal lines, etc). I find that the best people photographs often come from more spontaneous shooting.

And thanks to the advent of digital, a spontaneous style of shooting no longer carries the risks it used to (i.e. you didn’t get the shot!).

However I think your suggestions would probably still be of great use to beginners. Once they are confident and getting good results working with the ‘rules’ you have suggested, they would be well advised to experiment a little more.

Cheers,
Steven