First off, the CN9-AH was our test vehicle for what we could do for Yen-Lo Wang. It was the closest variant we would use without exposing what the first Hero Mech was going to be. Now that Yen-Lo Wang is announced and present, we have removed the CN9-AH and will be replacing it with the CN9-D with the Artemis Guidance System in the next Mech release pack.
As for knockdowns, they were broken... plain and simple. I had been asking for a while now to have them removed until we get both the physics and the network side of Mech movement down properly so it a) doesn't look horrible and

I'll check into the DHS system. Seems a bit light to me as well.