Liners are passenger ships. Only power it needs is to power the stardrive, life support, and nav systems. Weapons are a plus to defend until help arrives.
As an analogy? Have you ever seen a passenger vessel, like this one
carrying the weapons of this other one?
No. You don't.
And in fact, the Passenger ships are bigger, and have more power available. But they are just that. Passenger ships. Not bloody camouflaged planet killers. So get used to it. Liners will be liners, not super Uber small battleships. If you are looking for that, then this is not the right mod.
(If you find any mistake in my English, please let me know via a PM)
(Really, I speak terrible English, so please, tell me if I make mistakes. I'd like to improve it a bit )