If the World Wars are avoided, I can easily see Germany and Auatria going for closer economic integration. Parisan concerns (e.g. German agrarian land-owners opposing a common market) will be eclipsed by the benefits of (and ultimately need for) closer partnership.
This will most probably be a scenario in which Russia, with some hiccups along the way, becomes a real threat to Europe. The Austro-Germans will lend clandestine support to Polish, Finnish, Baltic and Ukrainian independence movements. This will presumably be in exchange for them joining an Austro-German led security pact. (And also accepting appropriately German-speaking monarchs.) The countries involved may well play ball, since being a sovereign country subordinate to Germany is still much better than being directly under the Russian yoke.
In the Balkan countries, it may be different. Bulgaria could go with the German system, but Serbia and Romania may well have serious objections. Alternatively, the Austrians may court the Romanians, but that may well lose them Bulgarian support. Greece will stay neutral at firm British insistence. But otherwise, if Russia develops into a real threat over time, Britain may tentatively start backing the Germans against the Russians...
All in all, though, we are talking here about some customs union at the core, with a hot of bilateral treaties for the peripheral countries, and then another slew of common security arrangements. And part of the above relies on the assumption that Polish, Finnish, Baltic and Ukrainian independence movements can succeed. Which may well be called into question.
So an alternative is that it's just Germany, Austria-Hungary, and either Bulgaria or Romania. With the Ottomans as a more detached ally. However, in that case, again assuming Russia grows more threatening as time passes, British support for the German bloc will likely be more overt.