Package external assets into project from other projects. Huge data sets

Our project has very large terrain textures and meshes. By large I mean the total texture files on disk are 15GB

We do not want all that in git (or Perforce) code control because if it gets revised then the git becomes bloated.
What we would like to do is have several UE4 projects, with a “main” project and then completely separate UE4 project, one for each scenario.
Question: How can on package a project and include content from another project without copying the content into the main project?