I've looked but am having trouble finding a preference or some other setting in Numbers 2 (the previous version) that allows remapping this key.
You can easily modify keyboard shortcuts for Numbers 3 for any menu pick just the way you can for any other OS X application via System Preferences > Keyboard > Shortcuts.
But what you are discussing here is not a keyboard shortcut. It's entering a specific character into text, not executing a command. Remapping your keyboard may do the trick for you. Have you tried?
SG
P.S. We're all just fellow users here. If you wish to communicate with Apple, choose Numbers > Provide Numbers Feedback in your menu.