I thought the Yi were in Jiangsu and Anhui as well as Shandong. (And I'm not claiming that they're nomadic)
Not sure about the Anhui part, but I think the Yi were in the northern part of Jiangsu, near Shandong, and Wu was founded closer to Zhejiang.
Qin's power base was actually to the west of Zhao's, and it relied more administrative and economic development (aided by geography that made it easier to defend).
Still talking about the (Western) Zhou. Again, this is also true, but the Qin capitals were located basically right next to the Western Zhou capital, and I don't think they were sacked by barbarians. Xianyang is basically right next to Haojing, and Yong and Jingyang were even closer to the territories of the nomads. In terms of defense, they seem to me to be just as hard to defend as the Western Zhou capital was. That's why I'm suggesting that a longer Western Zhou might see the Zhou house retain control in the west, with access to the geography that did help Qin, eliminating Qin, while the east of China would definitely see a Warring States Period.
Maybe, but I'm more interested in an "incomplete" unification of China.
Hainan is much closer to the mainland than the Ryukyu's or Taiwan. (Hainan is only separated from the mainland by a strait 19 miles wide, while the strait separating Taiwan from China is more than 100 miles wide)
Yes, which is why I'd imagine Taiwan would have an interesting history as a prison colony. If the Confucian literati dreaded going to Hainan, just twenty miles away from the mainland, imagine their dread at being sent to Taiwan (probably not going to be called that here) instead.