Why so hostile ? I am a trader too, 2/3 of the way to Elite done, still I enjoy the occasional interdiction and collecting the bounty. That's what I fly an armed Conda for, not a T9.
Yes, blowing pirates to dust is fun and brings diversity to trading. How I am supposedly somehow obligated to think 'Credits trump everything' just because I happen to be a trader is completely beyond me.
Sounds a bit like a food combining diet to be honest. 'You may eat the rice and then afterwards the meat, but it is ILLEGAL to eat meat and rice together'
@OP:
First of all, if you listen to this forum you might think in open it takes on average 4 seconds until you are violated by an angry flashmob of hacker-cheater-griefers. In my experience this is not the case at all. While I understand that ED has little potential for E-sports style competitive PVP due to how easy it is to cheat, you have to keep in mind that the vast majority of players in open are people like you and me. People that want to enjoy themselves a little bit and have no need to compensate for real life problems by being a jerk. Just avoid the general area surrounding Lave and you should be fine.
Secondly, this is my take on a lightly armed trading anaconda for open, which I personally fly at the moment and use to happily shoot down NPC pirates

:
- Class 6A power plant (this limits the options somewhat, but 7A drives the price up too much, bad for insurance costs)
- 7D thrusters, 7D power distributor, 6A frameshift drive
- Grade D sensors and life support
- stock fuel tank and hull plating
- 1 * Class 1 gimballed pulse laser on huge hardpoint (so you can actively attack other ships by poking them, which is not possible in an all turret layout, tiny weapon on massive hardpoint to save weight and because it looks funny)
- 3 * Class 3 turreted pulse lasers
- 2 * Class 2 turreted pulse lasers
- 2 * Class 1 turreted pulse lasers
- Class 4A shields
- 6 * Class 0A shield boosters
- 2 * Chaff Launchers
- Standard Docking computer
Result: 448 tons of cargo with jump range of 19.12 Ly at a price tag of 186 million. All of this is only marginally worse compared to a pure trading conda.