: The Twos had a fairly successful augmentation success rate, and that was only
: perfected for the subsequent companies of Threes. Concurrent to Gamma
: augmentations, perhaps, tests conducted by ONI may have proven that the
: protocols have matured to allow for adult augmentation without the
: complications seen with Orion.

From a storytelling perspective, you can also go the other way. You can easily say that some of the augments require the puberty process to take. So, if you're going to turn adults into supersoldiers, you need to go with fewer or less effective augments.

That, to me, would make for a more powerful discussion. In the coming wars, is our need for an edge so great that we can justify kidnapping children?

: In a strict warfighting sense, with no concern given towards who the enemy
: is, the Fours are an excellent investment. Instead of maturing a six-year
: old until age 14 or 15 in the rigors of combat, while stripping them of
: much of their individuality and potential experience, they get
: supersoldiers with immense background.

Said background led to defection and imprisonment in both Orion and the Spartan IV program.

: They're picked from a pool of
: billions, all volunteers, all successfully augmented with the same
: capabilities as their predecessors. However, their advantage lies in 17-20
: years of maturity, years on the frontlines as a regular troop, and
: experience in the field as special operations troops

Two things:
One, assuming that the genetic requirements still hold, you'll be working with a smaller candidate pool. You're no longer searching the general population for individuals with the physiology to survive augmentation, you're searching the Special Operations community for individuals with these rare genes. Good luck building a battalion.

And yes, I know that the Spartan III program had looser genetic tolerances. They were suicide troops. Being able to live for five years after the augments probably wasn't in the search criteria.

Two, while spending years as a meatsack on the front lines does bring about useful skills, there's got to be advantages to being trained for combat during your most formative years.

: The only training
: they need is acclimation to the augments and armor. Since they can augment
: so many Spartans and quickly transfer them back to the field, they'll need
: plenty of gear and mass production is kicked up lowering costs.

Economies of scale do not automatically make something affordable. If equipping the Spartan IIs with their MJOLNIR was on par with building a carrier group, building that same armor for five hundred Spartans does not make it any cheaper.