Like I said, I'm sure this has been thought through, but it still doesn't make sense. I wasn't thinking plug and play spare parts. More along the lines of "gee I could make this cool thing if only we had a few spare pieces of lexan" or "we might survive this very bad problem if only we had a few #5 bolts. That shuttle that used to be up here had hundreds, but now it's in a freakin' museum." I know NASA frowns on improvisation and using parts for things other what they were specifically designed for, but at some point we need to get over that.
Filling it with enough waste gas (space farts for all it matters) to maintain a "soft" vacuum for storage also doesn't seem like a big drain.
At some point it would a net negative for fuel. the additional mass is there forever, while the additional fuel left in the shuttle will be used up at some point.