While I agree with the first 3 paragraphs of your opinion, I don't understand why Yahoo HAS to acquire Google to make your argument count? NeXT was not on its way to become the next-big-one. It was mostly Steve Jobs who changed things at Apple with other people's help and contribution.
If Marissa Mayer is as good as the general consensus is and has built connections with all these other smart people, I don't see why it would be a surprise if she turns Yahoo around as a genuine competitor. I don't think that she has to achieve this via some 'coupe'. After all, Yahoo has paid her massive amounts. I am sure they believe in her and respect her decisions rather than be upset with it.
If Marissa Mayer is as good as the general consensus is and has built connections with all these other smart people, I don't see why it would be a surprise if she turns Yahoo around as a genuine competitor. I don't think that she has to achieve this via some 'coupe'. After all, Yahoo has paid her massive amounts. I am sure they believe in her and respect her decisions rather than be upset with it.