Well Helpinghans explained it in his last stream. There was a big discuss.
His answer: 2 Mortarpits are not viable. Just get more isg
Aka 2 mortarpits, get 3 isg then.
But not worth it to ban. I think people will/ can play around it. Also not everymap is great for that. Also its at vs at and not random.
ISGs only counter a mortar pit if they're in reinforcement range while able to fire at the pits, and they cant kill it through stand fast.
If the Brit player gets AEC before building a Pit they can position them how they want and then there are no counters, even Lefh cant do it through Stand Fast.
Banning emplacement commander legitimately makes no sense regardless as its the worse of the two emplacements commanders anyway.