"Implementing" async audio as a game properties option does absolutely nothing different for the underlying code. All it does is slightly change where it appears for the users, and how they'd enable it; everything else would be all but unchanged. It doesn't make it easier or feasible for the developers to implement. Since UI stuff is trivial compared to the actual implementation, I don't think this is really going to help your argument at all.
You'd have to ask someone else about the CPU wait thing; it's probably not feasible, but I'm not a programmer that really understands how the CPU emulation here works. I don't think you can just tell the CPU to wait and not expect to break things, but someone more knowledgeable than me would need to answer.
The last point about adding stuff to the game properties window gets more into Dolphin's UI a bit, and is mostly unrelated to the main issue at hand.
You'd have to ask someone else about the CPU wait thing; it's probably not feasible, but I'm not a programmer that really understands how the CPU emulation here works. I don't think you can just tell the CPU to wait and not expect to break things, but someone more knowledgeable than me would need to answer.
The last point about adding stuff to the game properties window gets more into Dolphin's UI a bit, and is mostly unrelated to the main issue at hand.