No, the *player* isn't afraid of Thrakhath... a main character who doesn't worry about anything isn't an interesting one.
True, Blair goes on about how he needs a wingmen he can trust, while all the Player needs is someone who draws fire and don't steal his kills.
I would argue that this isn't true - the three ships flown in WCIV can't be specific to the Union of the Border Worlds... because the UBW comes into existince *during* the game. They *must* be existing designs flown when the colonies thought themselves part of the Confederation (in fact, we encounter them all before the UBW is formed, early in the game).
I agree, the BWU cames into existence after the game begins. But I think they those ships specific to the Border Worlds Militia in some way. Seether uses Avengers and other BW craft to frame the attacks on the Border Worlds. Later, Blair & co remarks:
Maverick: Look, Confed’s a much bigger machine than any of us can possibly imagine. That bastard Seether – and whoever he’s working with – can marshal incredible resources.
Hawk: Sure: mercenaries, pirates, Confed craft, our craft…
Panther: The unmarked ships.
If the Player flies a Vindicator on Telamon, the colonists recognize it as the "Border Patrol".
Besides, I'd argue that the game itself makes the point there's more ships flying off the Intrepid than it's reflected in gameplay. When Blair lands during the fight with the Vesuvius, you can see a Vindicator landing on the flight bay.
I never had any problem with the novel using different ships. Even if no background is given, it seems there was no way the BW could have that many vindicators with apparently expensive and exotic light tachyon guns.