Theming layout of OG front page

I'm using Organic Groups on several sites in lieu of sections - because of the flexibility and membership options. However, I would like to have more power over theming the layout of the group pages. Out of the box, there is the option of displaying all posts as a river of news (blog style) and grouping the posts by content type. However, the second option seems to come in a predetermined format which is not suitable if the section should also present the group to the outside world. I would like to make the group front page look more like a dashboard (such as those using the Panels module). Unfortunately, it seems that it is impossible to theme that layout because the whole block is generated by calling $homepage_nodes. Any ideas how to change that view? I've also thought about using Views but, unfortunately, OG only provides filtering by groups the user is subscribed to rather than by what group a node belongs to. Which means I can't use the excellent Panels view to get around this. (Unless, I'm missing something.) I would be grateful for any hints of where to go next.