Vesicles mentioned earlier that both Jiang and Mao had Emperors' ambitions. I would disagree, on both counts. Jiang had the ambition of a warlord, and his actions demonstrated this clearly. He never did have the vision nor the ambition to rule over all of China. This is the guy who willingly gave up vast parts of China in order to secure his own rule.
As for Mao, his Emperor ambitions came later, after securing the rule of China and cultivating his personality cult. During the war against the Japanese, he had repeatedly called for a democratic two-party system.
Well, Jiang still aimed to be the sole ruler of a country, no matter how small the country is. A warlord would have no problem sharing power with others, like what happened in the Zhou dynasty with all the warring states. Jiang, on the other hand, could not stand the thought of sharing his power with anyone. Like you said, his primary goal at the beginning of the WWII was to eliminate his competition, be it other warlords or the CCP. That suggests he wanted to become the ultimate ruler. And his intention had always been ruling the entire China. He was simply planning to do in two steps: step one: eliminate all the internal enemies; step two: kick the Japanese out. Like I mentioned in my previous posts, Jiang believed that he would eventually get plenty help from the international community with fight against the Japanese. He, however, didn't believe that he would get any help at all when fighting his domestic enemies. So his initial priority was to eliminate his domestic enemies. Once that's done, he would then focus on the invasion. However, no one is fool. Everyone else knew about his plan. So the CCP tried their best to interfere his plan.
All in all, the fact that he wanted to eliminate his competition suggests that he wanted to be an emperor. Again, he would have no problem sharing the nation with others if he simply wanted to become a warlord. The only problem was he did not have the vision to complete his quest. I think it should be that Jiang had the ambition to become an emperor, but only had the vision and capability to be a warlord.
About Mao wanting a democratic govn't. I think it's all a gesture. At the time, Mao was the weak one. He was not even in a position to challenge Jiang since he was beaten badly and almost annihilated by the Nationalists. That's why he kept calling for a democratic govn't. He was simply begging the international community to put pressure on Jiang and to force Jiang to give up the plan to destroy him. Since Jiang wanted to look like a fair leader, he certainly could not flat out reject the notion of a democratic govn't. He would look bad in front of his international allies. That's what Mao was counting on. By calling for democratic gonv't, Mao was simply begging for mercy. Mao, on the other hand, would not entertain the idea of a democratic govn't when the CCP was winning at the end of the civil war. at that time, it was the Nationalists who called for a democratic govn't and sharing power in China. Mao did not even bother to respond to the call and simply sent his 1 million PLA to crush the Nationalists.