Not entirely unexplored:
Golden Century:
Era Digest: Golden Century
Proliferation Cycle: The Trickster
Dezgra (Shrapnel #9)
Half of a Warrior (BattleCorps)
Whispering Death (BattleCorps)
Turning Points: Tokasha
Political Century:
Emerald Sword
Scavenger's Blood (Shrapnel #2)
Seven Years' Bad Luck (BattleCorps)
Zeroing In (BattleCorps)
Way of the Clans
Bloodname
Exodus Road (Prelude chapter)
Jaguar's Leap
Fair, and you aren't wrong. Many of these are quite short though. Even
Era Digest: Golden Century only hints at a century where A LOT was going on. I wasn't suggesting there wasn't representation, there is, and I am grateful to the authors who wrote about these. It's just not in depth (and I think of the four novels you list at the end as more about the Invasion, than about the Political Century).
My emphasis was to express that it would be
really cool to see a few novels, a trilogy even, set in the Homeworlds before 3019 and the Dragoons resupply run. There's so much that happened from the death of Nicholas to the Dragoon Compromise that could fill whole novels.