Most Plausible Alternate Central Powers?

[Abdul Hadi Pasha]

On the subject of Italy, it's possible, but not likely. If the Schlieffen Plan works, then it becomes more likely.

The easiest alternate Central Powers is it's just Germany and A-H. Only one Ottoman wanted to Join the CP, but unfortunatly he was the war minister in a messy government. Everyone else, including the PM, wanted to stay neutral or join the Entente - until Churchill's horrendous blunder in appropriating battleships that were paid for by national subscription. If the Ottomans stay out, Bulgaria stays out. Without them, the war is a lot shorter.

As for other countries joining, the only one I can think of that's remotely possible is Afghanistan, if things are going really badly for the Entente - it would also require something like a Jutland scale German victory over the Grand Fleet and serious disturbances in India.

Another possibility might be China, but you'd need a POD that has a much more stable republic. China probably has more to gain against the Entente than the CP, but again, it would need the CP to be doing very well and something disastrous to happen to the RN.

 

[Abdul Hadi Pasha]

What was the Romanian reaction to being curbstomped by Austria-Hungary and Bulgaria?

And the Ottomans - they had a corps (about 40,000 men) of Gallipoli veterans in this campaign. That probably didn't make the Rumanians feel too good.