[All] How would you change things so that children of Zues & Hades were as powerful as Percy

Here's how I would change things:

Nico Di Angelo

Light/Dark:The more darkness he's in->The less energy is drained from him when he uses his powers (direct sunlight drains him as much as his powers already do in the real story and total darkness allows him to use his powers continuously with no drain on his energy)

Death:He receives a boost to his power (just like percy does with water) whenever he is near areas where a large number of people have died

His power increases

-The closer he is to an area where many people have died

-The more people have died in a concentrated area (e.g Hiroshima or Auschwitz)

-The less time it's been since the massacre (e.g Hiroshima/Auschwitz would provide more of a boost than krakatoa because the former was less than a 100 years ago and the latter was over 200 years ago)

-If he's in the Underworld he's at his most powerful and nearly invincible