I think the whole discussion or re-arming the Cobra is a red herring. It's been de-militarized to a far greater extent than just welding barrels and receivers shut. All the fire control systems are gutted of their insides and empty component boxes remain, too, so if you can re-fang this snake, you could use the same amount of cash, effort and new parts to turn any aircraft into a gunship. And whoever has the means to do that is smarter than trying it with a Cobra that is registered and watched by the FAA and DoD to ensure compliance.
I have an AK-47 that I could (but never would) convert to full auto in an afternoon. Why couldn't someone take a small airplane, like a Little Toot Biplane or a Steen Skybolt, and mount a couple full auto AKs on the cowl. Rig a couple trigger-actuated solenoids to fire them with a crankshaft-mounted interruptor switch and you can strafe some VIPs to get your name in the history books.
But folks like us would never do that, because we have morality, ethics and no reason to be so stupid. The problem is, a lot of those Islamikazes out there are smart enough to pull off something like that. But even the slightest whiff of Jihadi in their personal background check disqualifies them from buying old Cobras. Sometimes it's nice to have Big Brother watching.