Finally, i found the solution by myself.
openbase.com gave the crucial hint in point 3:
If you wish to include dependencies and use npm-pack you must do the following:
1. create bundledDependencies section in package.json
2. remember to update bundledDependencies before executing npm pack
3. remember to execute npm install before executing npm pack
Quite to my regret, the official npm documentation on bundledDependencies does not mention the neccessity to re-run npm install inside the folder of the node you want to bundle-package. This piece of information cost a noob like me ~14 hours of frustrated try-and-error. 
So, to spare others the same confusion about the behavior of npm pack, i suggest that a suitable hint be added to the npm documentation. 
Finally, to make things easier, i paste below a script i dug out that automates the entire process. The additional npm install step is yet missing in the script, but well,..
/*
* This script will download a package (and all of its dependencies) from the
* online NPM registry, then create a gzip'd tarball containing that package
* and all of its dependencies. This archive can then be copied to a machine
* without internet access and installed using npm.
*
* The idea is pretty simple:
* - npm install [package]
* - rewrite [package]/package.json to copy dependencies to bundleDependencies
* - npm pack [package]
*
* It is necessary to do this (intead of using pac) because when npm installs
* a module, it will actually strip out the node_modules folder from the
* tarball unless bundleDependencies is set.
*
* Author: Jack Gill (https://github.com/jackgill)
* Date: 11/27/2013
* License: MIT License (see end of file)
*/
// Original gist: https://gist.github.com/jackgill/7687308
// Slightly modified by @phillipj too enable specifying @version of packages
// updated by Dipl.-Ing. J. Menzel to fix broken regular expression and packet path resolution in 2021-2
'use strict';
var fs = require('fs');
var cp = require('child_process');
var path = require('path');
if (process.argv.length != 3) {
console.log("Usage: %s <package name>[@version]", process.argv[1]);
console.log("\nExamples:");
console.log("\tnode pack.js react");
console.log("\tnode pack.js angular@1.5.5");
console.log("\tnode pack.js @angular/core@2.0.1");
process.exit(0);
}
var fullPackageStr = process.argv[2]; // might include @version suffix
console.log("started with argv2: " + fullPackageStr);
// extracts package or @scope/package name, removing the possible @version suffix
var packageName = fullPackageStr.match(/^(@?[\w]+\/[\w-]+)|^([\w-]+)/)[0];
console.log("use package name: " + packageName);
// Copy dependencies to bundleDependencies
function rewritePackageJSON(fileName) {
var contents = fs.readFileSync(fileName);
var json = JSON.parse(contents);
if (json.dependencies) {
json.bundleDependencies = Object.keys(json.dependencies);
fs.writeFileSync(fileName, JSON.stringify(json, null, 2));
}
}
// Install the package from the online registry // npm install
var installProcess = cp.exec(' : ' + fullPackageStr, function(err, stdout) {
if (err) {
console.log("\n✘ Error executing npm install:", err);
process.exit(0);
}
else {
console.log("\n✔ installed package: ", fullPackageStr);
}
console.log(stdout)
// Set bundleDependencies for the package
rewritePackageJSON(path.join('node_modules', packageName, 'package.json'));
process.exit(0);
console.log("now npm pack: " + packageName);
// Create a new .tgz file which bundles all dependencies
var packProcess = cp.exec('npm pack ' + path.resolve(path.join('node_modules', packageName)), function(err) {
if (err) {
console.log("\n✘ Error executing npm pack:", err);
}
else {
console.log("\n✔ Bundled package", fullPackageStr);
}
});
pipeToProcessOutputs(packProcess);
});
pipeToProcessOutputs(installProcess);
function pipeToProcessOutputs(aChildProcess) {
aChildProcess.stderr.pipe(process.stderr);
aChildProcess.stdout.pipe(process.stdout);
}
/*
The MIT License (MIT)
Copyright (c) 2013 Jack Gill
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
