I have always found it a bizarre idea that we allegedly judge a country's importance by it's size on a Mercator projection map. Does anyone really think Greenland is the most important place in the world? Europe is tiny, yet the kind of people to complain about it will also complain about the outsized importance of it. Africa, which is apparently a victim of such projectionism, is also placed in the middle because of where the arbitrary Greenwich meridian goes.
Agreed - territorial area is only one measure of importance, and probably not a great one. What would be more useful on a wall, if we are interested in such things, are bubbles with size showing population, GDP, life expectancy, etc. (a la https://www.gapminder.org/tools/#$chart-type=bubbles&url=v2 ), arranged to preserve, as much as possible, country positions on the projection of your choosing.