In practice... Spam 10 layers of wall in the slaughtered canyon and build them. Spam some artys kill eveything in the canyon. Let the infantry advance (wall stairs) The arty shells the area where the engineers build new walls. Commander wallspams 10 layers of walls their. Do this til you get the middle, win. (you wall the bridge off too btw) If you have arty its not a problem to keep the canyon clear from infantry.
You do realise that that takes a lot of time, effort and devotion? That's like kursk defences you are describing. And what are my infantry doing in that time? Just standing around and waiting for the enemy to get artillery and build up their walls? Usually there are constant fighting going around, so i can't imagine that those walls would be allowed to be built unhindered. And it is a fact that when i get my APC those mega defences will not be operational. I have seen it dozen of times, APC will be able to breakthrough those semi built wall defences and push on, and meds will also. Or what will happen is that some people take three APC whit support rushes over the bridge deconstruct a hole and flood through. I have always won on slaughtered as commander by not going for artillery, yes my forces will have a hard time a minute or so untill we get APC weapons that allows us to just rush the enemy and kill teh artillery, and with APC spawn victory is assured.
Mayama, if it were impossible to break through walls that were fully built, Money would suck more than a leech. If you rush properly, it's hard to hold back. If you defend properly, it's hard to rush. Both require teamwork, the one with the most teamwork wins, the one with the least fails. that's all there is to it.
I think what Mayama meant is that you can't rush through them. If there's arty shelling your location, you're not going to be able to bust through those walls in time to do anything about it. And Money does suck more than a leech, and arty does generally win it, so...