Sounds like a good homework assignment...
As such, I'd make the student do his own homework and get him to approach the problem from both sides.
I'll keep my answers short and broad, as to not derail the educational value.
First off, if I went into business with someone and it happened to be a software business, they will be able to code and willing to code just as much as I am. Because I wouldn't hang around long while they sit on their ass while I wrote the code that made the money. I would set up my own shop before that lasted more than a day.
"Reimplement the STL? " -- No.
"Is that a practical decision?" -- No.
"What would you do in this situation?"
I would go to the STL site, google for documentation and see if it is a known bug. Due to the widespread use of STL, chances are someone has already encountered it and there is a fix, so there is no need to reinvent the wheel.
"...and how would you do it? (whatever you do)"
See above.