The optimal choice is that you would be diving a balanced rig in the first place. Meaning, in a single tank, there is absolutely no reason you cannot swim up your rig to a depth where your wetsuit has regained some buoyancy if you are properly weighted.<snip>Lets say that you are at the tail end of the dive (~1000psi in your al80) and you are starting to work your way up. Then the wing fails catastrophically (for example, you pull the corrugated hose off the elbow that is attached to the wing) and now the wing is venting all of the gas you have in there. Is there enough time to deploy a lift bag to use as redundant buoyancy? Or is it more likely that you will find yourself at 100ft before any corrective action can be taken?
Yes, there is plenty of time. I carry a pony when the floor is that far down as well as normally abiding by thirds. I can deploy the bag while heading down. I can normally fin hard enough to hold myself in place in the water column. I have practiced all those scenarios. And to go back to your first point; I estimate that wet suit compression causes a loss of about 20 lbs pf buoyancy by 100'. Do you dive cold water in a wetsuit? This buoyancy change is common for everyone I dive with. How are you gonna "balance" that and still descend in the first place?