I would assert the fixes needed aren't complicated, but it would certainly require a stripping down and total resetting of the system. They will just get bonuses until their rank matches their true skill.
What's wrong about this? Hell, i'm pretty sure i continue to play this game sometimes due to that fallacy If win 6 times in a row, no personal adjustment. And I think that would have a positive effect on the total number of active high rank players. How many games is a few? I believe over the years I've gotten quite knowledgeable about MM not only in HotS and can share my experience and what I think should be changed.