This might be a dumb question, but it seems to me that the achievement "I Smell Burning Redsang" can't be done if you follow the faction quest, as one of the first missions is to invade and occupy a system.

Am i missing something?

I Smell Burning Redsang = 

Win a game without ever capturing a system after a successful ground battle

Well, first think this is not faction specific.

Anyway it says that you have to won sithout capturing a system, but doesn't says anything about razin or pillaging it after a succesful invasion, as long as you don't get the system.

As final note: I'll be honest, I didn't earned it yet.

To be honest, the thought never crossed my mind that I could do it with another faction than the Hissho..

Welp, problem solved then! 

You can due with them if you never occupy. Only subdue or raze systems after winning an invasion.