I'm too new at the game to have a very valid opinion, but I don't think
there's any question that it would have a drastic effect on mobility.
Some players may already have started implementing strategies that count
on mobility being limited to the four compass points, and I am also afraid
that the suggested change would effectively "shrink" the world.
I personally am already concerned that the map may already be too small
(depending on the N-S dimension). But that may be simple paranoia.