Chief Helm Officer - Lieutenant JG Travis Mayweather - Human male, early-20s. A Boomer who has spent his entire life in space. He has more space hours, visited more places and witnessed more unusual things than anyone else on the crew and looks set for a very promising career in Starfleet. e.
Have Mayweather be a chief petty officer, "Chief of the Boat," anyone who knows anything about naval service know these guys are the true power behind the thrown. Senior NCO's will
pull an inexperienced officer (and a experienced one) to the side and spell things out to them.
Make Mayweather older, fifty plus, iron gray crewcut hair, Marine Corp fit, born in space, served aboard a dozen civilian ships, commanded a couple, multiple ex-wives and a grandfather too. His wandering feet have brought him to star fleet decades before, has a been there - done that attitude, he sometimes gets in Archer face with his greater life experiences.
Captain must first deal with one of his crew that he learns is a Eastern Coalition Terrorist and has sabotaged the ship
Instead of a individual, have it be a terror cell, that way you can catch one or two, but then more spring up. Have the Eastern Coalition aim be subtlety different than the (United Earth's?) aims, instead of a heavy handed difference. That way they can recruit from amongst the crew.