But still, adding
labor for people to do on-orbit is problematic.

So even aside from the issues specific to the shuttle external tank,
I'm not sure this is a promising idea.

Well, it seems this isn't a first idea...
http://www.spacefuture.com/archive/g...facility.shtml

of course, I'm no scientist, but it seems every hurdle has been looked at
except as you mentioned, the labor aspect.

I personally think the SIG concept of sending up a second ET attached in
place of the shuttle as a huge station itself would be
an attractive idea.