How to set up such a structure in Gulp?

Question

Building projects

There are many different projects arranged in this structure:

home --[
    -- project1
    -- project2
    -- project3
    -- project4
    -- project5

All projects have a single gulp configuration, but I would like not to produce a bunch of node_modules directories and move them to the root of all projects in order to get a structure like:

home --[
    -- project1
    -- project2
    -- project3
    -- project4
    -- project5
    -- node_modules

This was partially sorted out, but another problem arose:
We also download various css frameworks, jquery plugins via npm and they are also stored in node_modules, how can I import them into a sass file or use them when building? Is there a way to specify an absolute path? And what to do if the nesting of directories changes?