It is unlikely that any of you would have come across this advertisement. It is very industry specific and relates to the aerospace industry. The advertisement shows a DAC International's Gen-X Electronic Flight Bag in a fish tank with this wonderful catch phrase ... NOT THAT YOU WOULD BUT YOU COULD.
Now this can be used in a variety of scenario. Here goes ...
To the world leaders meeting at Copenhagen from today: Not that you would but you could [make the world a better place]
To the environmental scientists: Not that you would but you could [stop squabbling and do some real scientific work]
To Mukesh and Anil Ambani: No that you would but you could [stop converting your sibling rivalry into corporate war]
To the terrorists: Not that you would but you could [start behaving like decent human beings for a change]
You get the idea. The use is almost universal. An extremely brilliant, use-in-all-situations kind of phrase, don't you agree?
And finally to myself: Not that you would but you could [stop publishing such crap in the name of serendipity on this blog]