OK. However, could this ironically result in a better Russian performance in the Russo-Japanese War if this defeat spurs Russia to implement reforms?
Not immediately.
But, still, if the Balkans are blocked away from Russia's hands, the Tsar may decide to focus on Asia instead.
Wouldn't the Ottomans try joining the Franco-British alliance? After all, they wouldn't want to get dismembered by Russia, now would they?
If the ottomans believe they can hold out on their own, they'll most likely decide for a third-way position. But a british-ottoman "appeasement alliance" is possible if the ottomans decide to move into Egypt.
Aceh is very far away, no?
So was Amsterdam from Jakarta. What i said is that the ottomans would provide the acehnese with moral and political support.
If the Aceh War still happens ITTL, i'd expect the ottomans to covertly ship weapons to the acehnese and condemn the dutch in the diplomatic stage.
Couldn't Britain still make a move on Egypt in this TL, though?
While the Suez Canal was sure vital for communication with India, the british could estabilish sanctions and a blockade on the ottoman economy if Istanbul suddenly decides to nationalize the canal. Plus, re-annexing Egypt would mean taking over its debt responsibility.
Even IOTL, british occupation of Egypt was a hard task.
https://www.alternatehistory.com/fo...french-egypt-plausability-and-effects.315766/
Would Ottoman aid be enough to save any of these states (other than Ethiopia, which survived even without the help of the Ottomans), though?
Probably yes.
There's also the propaganda question -- with "a bunch of backwards mosulems", or the "sick man of Europe", defeating an european force, the ideology of the "white man's burden" would face dificulties in asserting itself.
What were the views of the Ottoman leadership in regards to federalization during this time?
There was the ideology of Ottomanism -- that the citizens of the ottoman empire were "ottomans" first and turks, arabs, bulgarians, greeks, albanians, bosniaks, serbs, kurds, and/or armenians second.
Perhaps it could grow if constitutionalism suffers no major blows. But it could clash with the aforemented "pan-islamic" policy, unless the ottoman government is good in rhethoric. Still, ethnic minorities would most probably decide to cooperate with the Sublime Porte at minimum and engage in peaceful "pride"-type resistance at maximum, as there would be no nearby european powers to liberate them directly.