While it is correct that Germany had problems integrating Eastern Germany and this had an influence on the later developments I sketched, they were different than you indicate. The relevant problem in this case was that in the takeover the GRD's currency had been exchanged 1on1 with the DM but without the economic backdrop that that would have required. This had weakened the underpinning of the Western currency but had not yet discounted into the exchange rate. So, when the DM entered the Euro the economy that had justified its relative strength was no longer structurally the same. Effectively the question at that time was, whether a country (in this case Germany) would enter at a rate that was higher and thus profit owners of capital to invest (outside Germany) or lower, which would have been advantageous for labor. We discussed this intensely at the trading desk and with people at the Bundesbank and on the board of Wise Men at the time. This problem was well known.
Having taken the easy way that seems to have been pushed by Mitterrand, a relatively high rate was signed off on. In effect this fixed prices for non-tradables within Germany at a level that meant the economy could not grow as quickly as it would have, had the currency fix been lower. German industry was suddenly less competitive, which does not mean it lost all exports, it just couldn't support the growth and jobs it was accustomed to, which translated into stagnation. This lead to investments in the rest of Europe, where the price of non-tradables was lower causing inflation in these countries and stagnating ones in Germany.
This is not the major problem of the Maastricht Treaty, which was willfully constructed in a way that would create such cyclical imbalances that must lead to crisis and damage as the could no longer be neutralized by floating exchange rates. Why build a currency you knew would not work? Because a number of the mechanisms required by a currency were not palatable to the peoples of Europe at that time. In effect the later crisis would be used to force the "Immer Tiefere Union" (always deepening union) as a fellow at the Finance Ministry formulated it at the time and later recurring in the Treaty of Lisbon in those words. Such deceit is not so surprising in EU matters. It is a variant of the Monnet Method which well known euroctatic procedure.
I have often found that the use of expletives by a person is negatively correlated with the quality of what he says.