Great job on the series.
I would make a comment on the difference between the first and second gear lists in that (it seems to me) the only real difference is in the fleece bottoms and the gloves for a real difference of only 3.6 ounces.
Why? The difference in the shelters really seems to be extra room. You could add the mesh and the extra beak to the single Hexamid shelter and have practically the same comfort level without the extra room (and weight) of the twin. You also wouldn't need a larger groundcloth. You could save at least 3 ounces with the equipped Solo as opposed to the Twin and achieve the same features of mesh and extra beak. However, adding the mesh and extended beak to the solo would put you a couple of ounces over the 5 pound limit.
Also, why a different water treatment system that weights 2.7 ounces more(including the heavier bottle required) that does the same job as the original system. You may prefer the Steripen system, but it does the same job as the Aqua-Mira.
Third, the different rainwear options may be a little more breathable, but, how often do we wear rain gear and really how much more comfortable would you be? The first system achieves what is needed without the extra weight.
So, now we can go to the third system. The third system of course incorporates the extra weight of the second class and adds weight for the pack, sleeping bag, sleeping pad, hat, and cooking system. This adds up to a total of 16.6 ounces if my math is correct. All of these seem to be legitimate weight additions given harsher conditions in the mountains.
Thus, given the comments above, the real difference between the first system and the third system is only 20.2 ounces instead of approximately 33 ounces. All of this weight is in improved clothing and sleeping systems from a temperature standpoint. This puts the heavier system at 6.2 pounds, just slightly above the second list. Also, this list is just as functional as the third list. Saving .8 pounds and being just as functional seems to make sense to me.
Just another way to look at the difference between the systems described.
Again, a great job looking at the system as a whole and thanks for the series.