RE: What did the Archon actually do and will it kill us?
Continued: Could Meridian be weaponized? Technically, anything can be weaponized if you throw it hard enough. Note: do NOT say that to Tann.
We're getting into "who are the Jardaan and what did they intend?" territory. Signs point to Meridian being a life-lab or seed world, and that includes aggressive terraforming through networked vaults. This could be dangerous. But while it is tempting to look at the "purge" state of vaults and wonder if that could be turned into a planet-wide event, we've seen no evidence of that capability.
(Do not send the below section to Tann. Not helpful.)
Some pedant says that ever since the 2037 outbreak on Earth, every military-run human lab has had protocols for emergency sterilization of facilities. Salarians have similar fail-safes, again in military facilities. Has anyone asked whether the Meridian sphere and connected vaults were considered "civilian" enterprises? We know that the Scourge was a weapon and that the Jardaan were deliberately targeted, but we've no indication why. Seems like we'd want to know that.