Christy,
I routinely re-wire the cord blocks. The older blocks are made better than the new ones. There is nothing unsafe about do it as long as you pay attention to the way they are wired and make sure there is no crossed wires.
Some people are just fanatically paranoid about things. No need for that. Just use common sense and caution and these things work fine.
Here's what a cord block looks like inside:
[ATTACH=CONFIG]513279[/ATTACH]
Here's one I rewired:
Before:
[ATTACH=CONFIG]513280[/ATTACH]
Someone jury rigged this one before. I have no idea if it worked
or not, I just tore it apart and redid it.
After:
[ATTACH=CONFIG]513281[/ATTACH]
Here's a new one I took the back off so I could label it for someone:
[ATTACH=CONFIG]513282[/ATTACH]
Joe