Tier 2 Retaining Walls

Currently Tier 1 walls have very limited use and get tedious to use on anything deeper. Suggest a Tier 2, 10 deep version.

I think stackable walls would work just as well. Maybe Tier 2 would be tougher and less breakable, and maybe wider so you can see the difference between T1 and T2.

The current retaining walls are an extreme hassle to use since they only occupies half a cell and dig/fill commands ignore the wall in the cell. One way to remedy this would be to add a new tier for retaining wall (or two) that fill an entire cell but are longer.
Example:
Tier1: 1x2x4 Made of Iron and Concrete (the current version)
Tier2: 2x2x6 Made of Steel and Concrete
Tier3: 2x2x8 Made of Steel, Concrete and Carbon

Going off of what Fenrir00 said:
1. Concrete
2. Concrete + Steel
3. Ferrocrete + Steel (Crushed Iron Ore instead of Sand)
4. Ferrocrete + Titanium
1. 2 less height than current walls.
2. Same height as current walls.
3. 2 more height than current walls.
4. 4 more height than current walls.

My additional suggestion is to allow us to use planning mode to put retaining walls deep under ground while building out a downward ramp or in the case of You Shall Not Pass map, going up the steep cliffs. It would be a bonus to allow those to come off pause when their space gets revealed as digging progresses. Ultimately, it seems silly that they "collapse" when buried. And, allow a little more flexibility on placement...sometimes I'll dig out an area, and a tiny little bit of dirt will be stuck to a retaining wall, not allowing an adjacent wall at all due to height differences.
Thanks!

If You want to deeper retaining wall, it is like magic. How you can put inside land? If we get it, it should by like another TECH. And with this tech we should by use same machinery for deep lay wall, like it is in real, Drilling, and use another truck for mixing beton.

2x2 walls could also be, or have a variant, that is flush with the ground, and can be driven on, as well as being buried, would allow ore storage pits to be more flexible.

It could be used to flatten the edges so we spend less material when filling and ports would look much better.

For me, "retaining walls 2" as a researchable item, where it has the following specs:
size: 10 deep, 4 wide.
materials: 4x the concrete, probably steel instead of iron.
This would allow creating a 4-wide, 10-deep slope which would be usable for deep mine pits. Without any walls, solid material like rock, coal, iron ore etc. sit on a slope of about 28 deep, 16 wide - the current retaining walls can be stacked 10 deep 4 wide but trying to go deeper than 10 leads to failures due to the way mining works. The suggestion above would allow for digging 10 deep behind a 4-wide wall, then installing another wall at the edge of the pit and digging 10 deep again.