In the aftermath of Leipzig, as the Allies advanced upon Germany, there were those who were thinking of the future of Germany. Among the concerns was the abolition of the tariffs and duties which had shackled Central European trade for so long.
There were a few proposals floating around, ranging from one for Germany (not established until 1834 OTL) to a wide ranging one, stretching from Amsterdam to Stockholm.
This is mostly woolgathering, but what would the consequences have been of such an agreement?