Good post. I understand you to be correct in that population is the largest driver worldwide in GDP. These arguments also leave out the very important fact that there is also a "quality" of the GDP pie. To get the fastest growing GDP pie you use wasteful methods and offload costs as much as possible. Working at increasing the quality of the pie can also create happiness. This would be such things as closed cycle production and minimal offloading of costs, etc. Not a larger pie, but a higher quality pie I believe would cause the most "Happiness" (not sure what to call it).
So true that quality is a better way to live! However, as it's measured, I don't think cheaper inputs to a product or service change the GDP. To avoid double counting they won't measure components made to become part of a final product that a consumer buys; they just measure the price the final product sells at. But, if cheaper inputs lower the final products price they will sell more units and thus raise the total GDP. Is that what you meant?
The theorybiz article has many of the items that I was thinking of, especially the increasing #scarcity. For example, the topsoil in the #USA is being depleted and is a positive in the GDP figures. Increasing the farming quality so that we have no net loss of topsoil should lead to the best possible results in whatever measure is used.