Hard to say really. I have a feeling things would drag on like usual. The Ausgleich negotiations would be painful, but in the end dualism would be renewed, the Magyars return to Budapest somewhat satisfied (convinced their demands for independence saved dualism, since the Austrians wouldn't dare offend them, and once again agreed to compromise). The Czechs, Poles and South Slavs would continue to grow restless and their demands would get louder. FF is just happy the monarchy didn't lose more power, is annoyed by growing Liberal and Socialist voices in Vienna but doesn't dare strike against them and hope the Conservative politicians will keep them down. It would give the Empire some time, but when the 20s begin, things would just keep deteriorating. In Hungary voices for universal suffrage would get louder and annoy the nobility, but meanwhile the regular Magyars agree with the nobles that the minorities (except in some few cases the Croatians) can't be trusted. In Vienna the demands for a weaker monarch would get louder, in Prague the demands for Czech autonomy will be heard on every street (while the German Bohemians start their own demonstrations against any form of Czech self determination), in Galizia the wish for Polish and Ukrainian autonomy is only overshadowed by the conflict between the Poles and the Ukrainians about who's in charge in East Galizia. Slovenians would get more anxious about Germanization, the Italian Austrians would start with their own demands too. But still, the best thing FF could do is just hope for the best, that it somehow will sort out itself. A showdown with Budapest could not only lead to a Hungarian revolt, but to other parts of the empire rebelling when they see the chance. Centralization would have to happen from the point of a rifle with blood on the streets in Hungary, Bohemia, Croatia, Galizia and maybe even the German speaking parts of Austria.
Edit: Although a unified parliament would be interesting, since basically it would claim to represent the whole Empire, but just the Germans would bother to show up. A federalized empire would also be interesting, but we shouldn't get our hopes up that such an empire would be fairly divided among ethnicities. Here is how I think a federalized empire would look like:
a) Kingdom of Austria: Austrian ancestral lands (modern Austria, Slovenia, South Tirol and Trento), Gorizia, Trieste, Istria. Known for: Germanization policies toward the Slovene and Italian speaking lands.
b) Kingdom of Bohemia: Bohemia, Moravia, Austrian Silesia. Known for: Ethnic tensions and clashes between Czechs and Germans
c) Kingdom of Galizia: West Galizia, East Galizia, Bukovina. Known for: Serious tensions between Poles and Ukrainians
d) Kingdom of Croatia: Croatia- Slavonia, Bosnia, Dalmatia. Known for: Masterly playing Vienna and Budapest against each other to achieve a Croatian State within the Empire. Tensions with Serbia over Bosnia.
e) Kingdom of Hungary: Rest of Hungary (only lost Croatia- Slavonia). Known for: Tensions between nobles and commoners. Tensions between Magyars and the Serb, Slovak and Romanian minorities. Magyarization policies.
The idea with the federal states is the divide and conquer principle. Each of the States except Austria is supposed to be weakened by internal strifes to hinder them from just declaring independence and secede. Further more Serbs, Romanians and Italians are just deemed to untrustworthy. Slovenians and Slovakians are not considered important enough, and you'd never get the Magyars to give up Slovakia without a fight anyways, neither will you get Austria to give up the ancestral lands of Carniola. And Austrian access to the sea would be seen as necessary. Another important factor would be that this could only happen if FF is pressured hard, and basically forced to agree to it (which is not that farfetched). A federal empire would be the death of the remaining powers of the monarch.