Seems not, but possible to implement?  Like nest a VFS in a file, inside a directory?

   How to get size?

// deserialize show file
bool LoadFileSystem(std::string FileName = "")
{
    if (FileName.size() == 0)
        FileName = "last.fs";

    ifstream in(FileName, ios::in | ios::binary);

    if (in.is_open())
    {
        in.seekg(0, std::ios::end);
        std::streampos length = in.tellg();
        in.seekg(0, std::ios::beg);

        std::vector<char> buffer(length);
        in.read(&buffer[0], length);
        in.close();

        try
        {
            g_VFS.Deserialize(buffer);
        }
        catch (VFS::CVFSException e)
        {
          //  spdlog::error("Failed to deserialize: '{}' -> {}",FileName, e.what());     
            return false;
        }

        return true;
    }

    // spdlog::error("Could not open file: {}", FileName);
    return false;
}