i think u categorized " hashirama's era " wrong because i feel that era should not be title hashirama's era because albeit his role in that era was significant he still had someone in that era that was just as significant and that person is Madara Uchiha, so thats era should be titled " One Dream " because thats what they had at the time was one dream which was creating the village...
also if i had to pick and era it would be madara's and hashirama's era because it would be more interesting and in the end it has more answers, although the biggest answers will be answered in the sage's era but his era is too bland for me...and u should have listed other era's such as " Hiruzen's " which would probably be the best and most satisfying era because it would give insight on " prime " hiruzen, the death of hashirama/tobirama(more) and danzo's growing hate for hiruzen, as well as building uchiha coup, and end of the 2nd world war and the 3rd world war/hanzo and the sannin