I looked at the code (have not run it yet). Nice. Well documented, clean. The design seems sound. An up/down section is also handy.
Shipping a default config would be nice, maybe in the /usr/doc/net/examples? A little heavy on the bash code for my liking, but I understand why. Have you mailed the maintainer of the netbase package (which provides the functionality you are replacing, I believe)? He may have suggestions. Short term solution, remove the network script from your package. Inform the user that they must edit /etc/init.d/network, you can provide the script in an examples directory in /usr/doc/net.
