I suggest to restore the mapgen V5 in the following Minetest version. It was interesting, because it was 3D noise.
I found these landscapes has a somewhat wonderful thing. I've played many times in the same world. But I had the bad idea to continue playing on it with Minetest 0.4.8 last year, and with mods, for example my Forest mod, carts and animal_modpack. Now I have a foolish map. But I've preserved the seed.
If I want to restaure this code, it's not only for me, but by thinking about this world, and this mapgen, I've realized it was actually very interesting.
The better place which remains of my world : this mountain has 94 blocks height. It doesn't exist in mapgen v6.

The official mapgen v5 screenshot :

There are 2 ways to do it :
First, we can translate it in LUA by lua voxelmanipulator and publish it as a mod.
Or we can put it in default mapgens (like v6, v7, indev and math) for the following Minetest.
I haven't a very good knowleadge of the C++. I think I can do the first thing, but not the second.
The code can be found here.
What do you think about it ?