If you think about it, mechanecologies are the ideal terraforming tool. Feed it the dust of an asteroid belt to get it started, point it at the planet you want messed it. Those mechanisms can evolve what's needed within decades if not years (a substantial improvement on most methods of terraforming!), and begin raining beasts down upon the planet. Then you just let them self-replicate for a while, and soon you'll have millions of properly-tuned space habitats!
...What do you mean, you want the planet to still be around?
