Neither War Monument or Mage Guild Round 1, Airships round 3 and no militarization before erosia, and no succubus temple expansion before gawnfall are the main fails some not so important checks to buy better investments optimizations I've seen discussed recently.
That could certainly free up enough resources to do keranii and open the ruins before the war though.
But I'm not going to commit to the skipping donovan work round 1, or insufficient airships erosia routes too hard before the suitor scores or Elves assisting with aram switches get used. We have no idea what consequences that will have yet.
Skipping the Succubus Temple Expansion on the other hand seems pretty safe as long as your Priestess Scores are still good enough for gawnfall, but I'm not sure if that alone is enough to make a keranii + early ruins route viable