A. The Ottoman Empire basically did in 1700 already.
B. Agree with Sian.
C. If Muhammad Ali succeeds in thrashing the Ottomans and westernizing this is easily doable.
A.I can't find a good map that shows the Ottomans ever controlling the entire Black Sea coast. Most show a gap in the Northeast corner in 1700 controlled by the Circassians.
C. The Sudd would still be a pain in the neck going upstream and once you go from OTL Southern Sudan into Uganda, it seems like it would be quite difficult to enforce control, though the British certainly succeeded.
A. Hunting around for some maps, it looks like despite the Turks not owning anything inland they did control all but two port cities on the Circassian coast. Additionally the Circassians were nominally vassals of the Khanate of Crimea, which was in turn a vassal of the Ottomans. I think that counts sufficiently as "control"?
C. If we're going full on Muhammad Ali-Egypt wank then Egypt is modern Western industrial country that just happens to be in Africa. It's easily doable with a PoD in 1700.
A. Yes, I see that as "enough" control. And then the question is did the PLC or Moscovy wreck it first...
An Egypt that controls Lake Victoria is going to be up there with Russia and the United States in Land area, I think. The only question is who can manage to pull of resisting them, Zanzibar, Magalasay?
For B the Habsburgs controlled a hell of a lot of Italy including the Kingdom of Naples. Have it stay with the Austrian branch rather than return to the Spanish branch after the War of Polish Succession. Add to that a conquest of Venice (not impossible) and a few victories in Northern Italy and they can easily have the Italian side of the Adriatic sewn up by 1800. The Balkan side is going to require multiple wars against the Ottomans and would be more difficult but not impossible. While Austria was on a downward slope post 1750 the Ottomans were on a steeper downward slope.
With a POD after 1700, which of the following seems most likely:
A) A single power controlling the entire coast of the Black Sea
B) A single power controlling the entire coast of the Adriatic Sea
C) A single power (with a capital in Africa) controlling at least 90% of the Nile Basin)
The question is, how do you get the Adriatic coast of the Papal lands?