I really like the approach to overlay/underlay stuff -- an elegant solution to what has been requested. It's not stated explicitly, so I'd just like to make sure: the overlay/underlays are visible to everyone without being sent like image(), right?
Second, I don't really understand what this means, though it sounds promising. Could you provide more explanation?
The dmp format now supports multiple turfs. All but the top-most turf (along with any icons) get converted into turf underlays.