Piotr, this would be an awesome feature. I'm new to Orchard and having a GUI placment.info for creating my theme would have helped a lot.
Features I'd like: Being able to select a shape when viewing the website (similar to Shape Tracing Module), then seeing a listing all the available shapes, allowing reordering, hiding, and showing.
It would be nice if it could work inline like the Shape Tracing Module does. Or maybe it could be on the Shape Tracing module in the placement.info tab.
I'm not sure how to handle the filtering - maybe you have ideas on this already. Maybe drop downs for displayType and contentType, and a textbox for path with a checkbox to filter by path or not defaulting to the current path.