Hi - this is not a bad idea, but the absolute *most* effective way to mount public objection to the ridiculous 30-hours-off-feed Standard is to get more submissions into the public consultation.
Creating a petition might be a GREAT way to raise public awareness about the issue (and this is very worthy in itself!), but I'm not sure how much weight it would hold in terms of the consultation, as it's clearly marked out how people should submit to it.
However, I have a slightly different idea that might work for you!
On this page we have outlined the key points and how to make a personal submission:
www.animalsaustralia.org/features/bobby-calf-public-consultation.php
On that page we also have a sample submission. If you wanted to get lots of people on board quickly you could print of the sample submission in a letter format, and just leave spaces for people's name, date and address. Take these pages out in place of a petition and ask people to sign them - one page each. VOILA! You could then send them all in together. I think that could have a huge impact!
Good luck! And thanks SO MUCH for wanting to help the bobby calves!