Try this one..
You are among the people on one of the twenty or so
Generation Ships that escaped the solar system after the last wars. After many long and fruitless centuries the
Singing Soaring Lark and it's crew have found a terraformable world. Tests show that the local life forms, all primitive single celled organisms, will be wiped out by bringing in Earthlife forms (yes some say it's wrong, the vast majority say microbes have no rights).
Now a new struggle begins, what will be the form of the new society?
Basically, it's a remix of
Alphacentauri. With the weight towards
Social engineering.