Wow, on a glance that paatch looks totally great.

A few quibbles about your use of whitespace: In comments, we've used "# 
xyz" not "#xyz" as you do (the difference is a space character). Also in 
templates we generally do {{ xyz }} not {{xyz}} (again, more space). If 
you make those chanes as a patch on top of this, that'd be swell.

I was hoping the project of achieving this could serve to help someone 
write a tutorial on doing this, so that there is a walkthrough on the wiki 
of how to use South to add a column.

Writing up that doc is a separate issue. Once I'm not on my phone, I'll 
give it a more thorough review (bit it looks fine now).

If you need suggestions for what to chew on next, let me know!