Place him behind ulrich. After he ults both he, and the unit in front of him can cast their ult without using any AP

Charon makes the dynamo rotation way more flexible and quick. Basically

Round one: 1 lucy skill, 2 ulrich channel, 1 charon buff

Round 2: charon ult, and try and get lucy to her ult by round 3
Round 3: ulrich ult, charon buff, lucy ult, spam lucy skills
Round 4: continue spamming lucy skills/ult and use the free ap for ezra if you want

Everything on the field should be giga dead and if it miraculously isn't , repeat the cycle, casting charon's buff every 2 rounds. His buff basically does insane overflow critrate to cdmg conversion.