I think transports have enough firepower as they do now. If they get stronger, people are going to do what? We're going to begin seeing transports in battles.
I've got a trader and I was always satisfied with 7 class 7 turrets and I think that's a fair amount of firepower.. And even with weaker traders I was able to make money without too much problem.
The problem is, everyone wants to play and never die. But its the way things are working. Fighters kill fighters and bombers. Bombers kill transports and kill gunboats in group. Gunboats kill freighters, bomber and fighters. and bigger ships kill anything except if there's a ship bigger than them. That's how things should work.
To me, it's like people are used to play single player games where they are owning everyone because they're the main character. So it's not important even if they're only one guy vs an army or a huge battleship. The enemy's going down no matter what. But here we're playing roleplay. That means you're going to get killed by bigger ships if you're flying a fighter because that's how a fighter roleplay is.