With all the talks of the Lucian alliance attacking Earth soon ,Instead of waiting for LA Fleet to show up or some small cargo ship carrying naquada bomb blowing up our city .
Earth could build Nanite weapon (Replicator) , not as first weapon , but the last weapon (doomsady weapon) a deterrent with the promise of retaliation and mutually assured destruction (MAD).
We don't use Nanite weapon as first weapon for war , because even with built in safety protocal ,or replicator disruptor weapon, the Replicator evolve and adapt too quick.There is no guarantee of controling them once your enemy are all dead.
In real life, Earth's countries spent billions dollar to develope nuclear weapon, and almost no one use it. Because it is the last resort. and deterrent.
Do you think North Korea would do all those cazy thing in the last few month if they didn't have the A- bomb.
China's entire ICBM missile force has less fire power than a US nuclear missile submarine, and yet it is enough as deterrent.
Some people even beleive China's project 863 is building nano weapon as the last resort.
And the IOA had already tried release replicator into Ori galaxy (movies :Ark of Truth )
Earth would send the Lucian alliance a message, if the LA attack earth or some cargo ship carrying naquada bomb and explode in any Earth city .
Earth will activate the nanite weapon store offworld , and slowly eat and destory the Lucian alliance planet by planet.
some one is carrying a box of inactive nanite off world, if they don't hear a message from Earth once a while they will activate the nanite .and so on.
Earth has came a long way in the Nanite technologies.
Earth has power to create nanite weapon (like the Replicator), some earth scientist outside the Stargate program , had already successfully creating humanoid replicator.(without using any Altantis's equipment)
IOA people already created program to build larger size bug Replicaor with resistance against Replicator Disruptor ,and buildin safety disarm signal.
Dr MaKay had successfully create Fran" ("Friendly Replicator Android") to destory the Asuran, and got a copy of orignal Wraith computer virus used aginst the Asuran.
SG1 also encounter Goa'uld nanite , and the nanite use for enhance learning.
But no one can really be sure of they can still control them if/when the nanite evlove .