I know there is a desire to make unique flora and fauna as much as possible, but what of humanity's old frienemies? We've historically been absolutely terrible at not shipping rats, mice, roaches, mosquitos, etc unintentionally all over the world, and our habit of accidental releases is not much better (wild pigs/boar, rabbits, nutria, feral cats eating local birds, etc...). Ye Ol' earth pests are uniquely suited to thrive in locations humanity would presume to call home for precisely the same reasons we would. While I am sure there will be other alien creatures that fill similar niches, how likely is it we will see a good old (space) rat tussling with it's local equivalent over in the gutters of Arc Corp and other human settlements?