The only issue I see with kbin itself doing that by default is that moderation might get a bit weird, as there would be no one team responsible for the page, while also complying with all the rules that might apply from different communities could also be problematic.
At the same time creating a post would be weird, if those communities are treated as one then where do you create a new post? Obviously not on all of them at once because then there will N posts in the "front page".
Perhaps having the ability to group magazines and read them as one would make sense, but i don't think it should be the default.