Thanks for this great mod!

Playing around with it locally (dev branch and stuff) and ran into sand-3 (at least) not being fully interchangeable with landfill in that you cannot pave over it.

Is this intentional for some of the custom landfill variants?

Looks like the following can't take pavement:
local terrains = {
"dry-dirt",
"dirt-4",
"grass-1",
"red-desert-1",
"sand-3",
}

The more I think about it, the more I think this is a 2.0 only problem with the changes to how landfill works and the dev2.0 branch. Feel free to ignore if it's already in-progress!

Hello,
I found a fix: In data.lua, in the last section, change the

for _, v in pairs(allterrain) do
data.raw.tile[v].can_be_part_of_blueprint = nil
end

to this:

for _, v in pairs(allterrain) do
data.raw.tile[v].is_foundation = true
data.raw.tile[v].can_be_part_of_blueprint = nil
end

EDIT: The two data.raw commands need to be indented. The forum doesn't show indentions correctly...

That fixed it for me.
I'm gonna open a PR for the 2.0 branch so that it gets fixed upstream.