How does CID help in combat when called to be a follower / homie?
According to the CID entry on the Saints Row 4 wiki,
As a Homie, CID does nothing to help The Protagonist in any way, he only speaks and has homie conversations, he does not fight in battle but follows the boss around. He is seen using some sort of weapon in cutscenes only.
So CID does not help in combat, and will only follow you around and have hilarious dialogue with your other homies.