> economies actually have a lot more capacity to absorb extra money than people think (many people are spooked by cases like Zimbabwe and Venezuela, whose problems in reality were caused by completely different factors)

The critical thing to understand these cases - and Weimar - is that you can't print foreign currency.

What happens in those economies is that the balance of trade worsens dramatically, but either people still need imports (oil, pharmaceuticals, spare parts for industry) or in the case of Weimar the country was obliged to export gold by the reparations treaty.

So prices of imports or import-dependant goods rise; the goverment prints money to try to keep up, but since it can't print exports or forex this doesn't work.

(I'm not sure whether your PV=MQ argument is precisely correct or if it overlaps with IS/LM, but it's broadly right)