IMHO it's a really good idea to create such a discussion group. I would be happy to be in.
I took a look there but I feel that creating a google account is not a good idea, as they are famous for abusing the information they collect about their users. And I'm not willing to visit a propriety website to take part in a discussion on open source themes.
Is there not a better - more technical - place that could host the group. The format should be a standard newsgroup (preferred), a mailing list or a website based on a standard GUI system such as phpBB