Don't know whether that Garrison Church should be rebuilt. As for Dresden, guess you mean the Frauenkirche (Lady's Church) in the old town - that was a little different. The ruins had been a monument for peace and reconciliation for a long time; the GDR even issued a 5 Mark coin, to commemorate the bombing of Dresden, which depicts that monument.

At that time, in 1985, there had even been plans to rebuild the church, also because many of the original material (which was still in and around the memorial) had begun to deteriorate. And quite a few in the GDR, even in the government, now had a different approach - at least the "important" old buildings in "important" cities were to be rebuilt. Whether the Lady's Church would have been a top priority, I don't know though.
The Garrison Church in Potsdam ... if they want to demonstrate what an important role the military had in Prussia, maybe they should build one again. As long as they do not spend my tax money on that, fine with me.
As for portraits on nazi coinage, well, shortly after Hindenburg died, Nazi Germany began issuing circulation coins with his portrait. Millions of Hindenburg 2 and 5 RM coins were made, for several years, until WW2 began. Guess that was a welcome reminder of how "legitimate" the new regime was, since Hindenburg was the president who appointed Hitler.
Don't think that Hitler was against the idea of having a Hitler portrait on coins - after all, many medals, donation tokens and postal stamps had his mug. However, when he started the war, it would have been too costly to issue millions of silver (or even gold) coins featuring the Führer. The alternative would have been to put him on a "cheap metal" piece; guess he would not have appreciated that. So the official idea was to have Hitler coins after the "final victory" ...
Christian