Can a hero on any sized base be part of a friendly unit?
For example could a Saurian Veteran on Tyrannosaur be deployed with a unit of Geckos, or a Necromancer on Ghost Chariot be deployed with a unit of Vampire Knights? I understand these examples may not be optimal, but it's more of a clarification question.
if you want to, yes. long as it has the Hero keyword
As an extension of the question, if a hero with a spear is set up in a unit that doesn't have spears, does the unit benefit from the Phalanx special ability? I don't think so, but it was a question in our group.