Deeper Retaining Walls like "Larssen sheet piling"

Retaining walls like "Larssen sheet piling" that can be 20m deep, need to be set with a maschine that looks like the treeharvester. No Concrete needed but more steel.

or a bigger version of the ones already in the game that take up the whole 4x4 square thing and go up to maybe 10 layers of holding
maybe this is mid game game and those are late game versions

double height retaining walls would be an excellent mid - late game fun!