Guys, either I'm too drunk (on coffee!), or I solved it without the
add-in. I recreated the solution in a different (upper) folder than the
website. Same for the project dependencies - different location and same
for the web setup project - upper locations than the website.
(upper location means in the folders hierarchy it;s closer to root (root
is d: in my case)
Somehow with this configuration adding a non altered 'web setup project'
worked. I now have a 300kb install with only the right things in it
(except for a subfolder that is not created anymore, and it should be in
the virtual dir). I'll go celebrate by getting drunk properly.
VS.NET was always very weird for me anyway (I worked with borland tools
for a few years).
Thanks to all of you who replied - the links info and filters are good
to know things.