Have you given any thought to how will the update be invoked? I mean, practically, the staff are vacating because of a fire - do you have someone nominated to “hit the switch” to make that change? You’ve mentioned that staff may be mid-call and so I expect you want the change to be immediate - but I can’t imagine anyone still sitting there, saying “I’ll be out in a second guys - just got to log in and update this Strategy/Block…”
Maybe a password-protected “Kill Switch” in IW/GSD?