Your suggestion could lead to shove being abused even harder then it already is. We seen from DOS2 how creating a ice surface and chain teleporting enemies into it to permanent stun lock cycle with 4 airomancers was busted beyond belief.
Here every char can shove, so it would be even worse then ddos2 as there is no cool down on shove.
Ideally we would remove difficult terrain in the first place. I always found this a bad gimmic. You should be playing smart, not using difficult terrain to cover for sloppy position and poor decisions [yes not everyone uses it this way. But I find it is used to easily as a cheat card]
