Forgive if this has already been raised (recently), but the search feature hasn't turned up anything for me so far. Basically as it says on the tin; how/why/what needs to happen to get to a successful German Confederation, that includes both Austria and Prussia, as well as the 'minor' German states.
Note that successful could mean becoming the European hegemon, or it could mean not being eaten alive by France in the West or Russia in the East. German Confederation likewise is open to interpretation, though the OP's preferred route would be through a successful Frankfurt Parliament, I am open, willing, and indeed hoping for other ideas as well.
As well, what, and why, happens after a successful 'Germany' comes to power roughly several decades ahead of IOTL, and one that is both larger and slightly less northernly-centered on the European continent? ex; IIRC, thousands of middle class liberal Germans fled abroad, especially to the United States, after the failure of Frankfurt; and many thousands more after the Austro-Prussian War. Presumably, unless a Civil War were to occur (again, how, why), the POD would butterfly away both of those events. How does this one small change affect history?
EDIT: As well, what would be the capital of such a state? Obviously both Berlin and Vienna are equally unacceptable to the Austrians and Prussians, respectably. If we take the Frankfurt successful route that city could be the host, but I could see this being argued against both because Frankfurt is within Prussia and because it is so close to the Eastern border. AFAIK, the capital would most likely be in one of the free cities (Frankfurt perhaps?), OR the capital of one of the smaller German states (Munich?)
As well, how does this affect Colonialism? With a *Germany more focused on Europe, what colonies does it acquire (when, how & why), if any at all. How does the other European powers react? Does this *Germany hold onto Trieste, or does it finally fall to the Italians?