Lets not fall into the same traps as the Rags and whole host of other clubs who give the top job to their past heroes. They invariably fall short, very few legendary managers were big name stars for their club as players. I know there are a few exceptions (I wouldn't count Keegan at Newcastle, maybe Dalglish part 1 at Liverpool but definitely Cruyff at Barca and Ajax).
If Kompany continues to improve for a couple years and then continues his development as a number two for us for at least two more then it is worth considering. Anytime sooner will be an emotional mistake.