I have come to the conclusion that it will take only six, thats rite SIX units to be able to cover every spot on the map within 1 year. that is, if you control these 6 spaces on the board, and you have an unobstructed line to the destination, you may get there by the end of the year. These spaces:
Fleets: MAO, Ionian(givens), Constantinople(for Black Sea), the skaggerak, (for nothern seas).
The two armies are positioned in Marseilles(for Munich, Paris, ruhr), and Galacia (for all of Russia, Balkans, AH, half of Germany.