If the elbow pops off the wing when you hop in the water, you're goin down. That simple.
A friend of mine had a rocket ascent to the surface when his wing inflated. All the way up. And that was just with one wing. It happens fast.
Isn't the normal thing when you hop in the water to be going down anyway? I'm not trying to be snarky. I'm just saying that, generally speaking, when I splash on a technical dive, I probably wouldn't even notice if the elbow popped off until I got (almost) to the bottom anyway. Meaning, when I did notice, I would have plenty of time to address it without being in a huge rush.
When your friend corked, did his wing inflate unprovoked? Or did it inflate after sticking, after he hit the button? In other words, at the point where he realized he needed to disconnect an inflator, was there any doubt regarding what inflator needed to be disconnected (or, would there have been if he also had a second inflator)?
None of that addresses the question of simply having the 2nd wing hooked up, if it's the kind of dive where dropping straight to the bottom would be a real problem.
What if you connected an inflator to the redundant wing bladder and put an inline shutoff on it?