Well, by definition the pimp my deck idea will involve a before and an after. All you need to do is add an explanation of why you suggested the changes you did, and maybe (if possible) a generalization of why the new deck is better at the end (or what philosophy got you from point A to point B), and you've basically got it.
For example, even if all you did was replace cards with similar, more efficient cards, that in itself could be a lesson. If you're having trouble ending with a generalization, I guess I could supply those.
"Scissors are overpowered. Rock is fine." -Paper