Like @lowwall says, since the OP has a drysuit, the notion of redundant buoyancy in the form of you/your buddy having a bigger wing is trying to solve a non-existent problem. If any of your wing, your buddy's wing, your drysuit, or their drysuit (if they have one) fails, you already have options.
When diving wet, your point stands better I think: diving wet with too much negative gear can make a wing failure dangerous. Which is exactly why most folks do not recommend diving heavy double tanks with a thick wetsuit. In that gear config, a lost wing can make a diver so negative that they cannot swim upward. And if they ditch weight, then they may soon find themselves in an uncontrolled ascent. However in a single-tank config with remotely good weighting, even the most out-of-shape diver should be able to swim up a single tank, keeping in mind that as one ascends, the suit will help them as it expands. A drysuit handles that case nicely, since you have ready access to a redundant source of buoyancy.
Still, even in that case, the bigger wing argument doesn't seem to work very well. I'm not a tech diver or an instructor, so someone can correct me if I'm wrong here, but I don't think that slapping on a bigger wing to negative rig + thick wetsuit config solves the problem very well. Imagine that you and your buddy both have huge wings. If your buddy's wing fails, they will suddenly become very negative. Hopefully you can go to them, grab onto one another, and inflate your wing enough to allow you both to become neutral -- whew! -- and then begin your ascent. The problem here is that if you and your buddy become separated, your buddy will descend rapidly while you ascend rapidly. You can no longer help your buddy, and you have a good chance of getting bent or embolizing yourself.
