First off, I am with Shi Tong on your first point about pointing out the original poster's problems with the English language, it's a bit unfair. And while it may be a bit hard to read, it's not worth chastizing someone over it. Just chiming in on that, Jiang Zhi, not trying to gang up on you
I know that you are a good poster.
Now, on to the topic. I may be wrong here, but did Cao Zhi even show much intent or any interest for that matter to become the heir to Cao Cao? I remember reading a fair amount about Cao Zhang wanting to challenge Pi on the succession (or in actuality the adversity between the brothers was brought on by other officers in the court, IIRC), but I was not sure about Cao Zhi. I may very well be wrong here.
Cao Pi seemed to be the born leader type, even though he certainally wasn't the wisest ruler, or the most clever, he did seem like a born leader regardless, and he most certainally wasn't a stupid man. It seemed to me that Cao Zhi showed signs of incredible intelligence even at a very young age, but from what I am aware of, he did not seem like the type to lead a very powerful country on his own, nor did he hold the ambition to do so. Plus, didn't he have two very influential friends in the Wei (or pre-Wei) court, and was very fond of wine?
I actually have more questions on this particlular subject than answers
Very good idea for a thread.