That would be a pretty big change though. Completely destabilizing in the Pacific. Destroyers would be extremely valuable. So many times I’ve cleared a Japanese destroyer and moved my whole fleet into SZ 6 in non-combat.
And it would change the ground game a bit too. I can remember a few times when playing as Germany when in Russian territory, and many times playing as Japan when fighting in Chinese territory where it was useful to use some infantry to take a territory and then move ahead two spaces with mechs/tanks into a friendly territory.
Also imagine playing as the UK and you decide to attack Iraq, but leave 1 mech behind to move through in non-combat to activate Persia.