I totally agree, I definitely implemented the 3/4 segment width road thing incorrectly in the track editor.
Kind of a tangent, but have you ever heard of or used Bob's track builder?
http://www.bobstrackbuilder.net/
It sure looks cool. I was going to have a look at the files it outputs to see if I could write a converter to VDrift. The only thing I don't like about it is it costs money, so in my mind it's more of a modeling tool than a proper track editor.
I was also thinking more about rewriting the track editor with a normal GUI toolkit. Any thoughts about improvements in the general workflow?