There is one attacking advantage to this setup that is useful, but you may choose to make it illegal because it really helps the attacker. Lets say I was the Russia player with 20 tanks and 20 infantry in Caucasus. Under this system, I could attack Ukraine with 10 tanks and 20 infantry, and if I win the battle, I could then take the remaining 10 tanks still in Caucasus, move into Eastern Europe, and attack that. However, once a unit has been declared an attacking unit in any territory, it may not attack in any other zone. Simple enough, isn't it?
O.K. That works all fine and dandy on land, but on the high seas it gets a little more complicated. Scenario: I am the UK and I move into the Gibralter Sea Zone with two battleships, three subs, and a carrier to attack it and take it from those greedy Germans. This was only one movement on all my ships. If I take it over, I then should do my non-combat movement. If I chose to leave a battleship in the Gibralter Sea Zone, and then want, on my non-combat movement, to move into the Southern Europe Sea Zone hoping to wreck the German transport capabilities to Africa. I ask, "Is there anything in the Southern Europe Sea Zone?" If they say "yes", I have no choice but to attack again. This is an advantage to the defender because if the attacker loses a lot in a battle but wins, and then tries a non-combat movement and runs into more of the defenders fleet, it might be destroyed. The attacker must be careful to avoid this.