Trails: I'm not sure if it works in the Molehill API, but you could do the old Processing trick. Before each render context3d.clear(red, green, blue, alpha) must be called. Perhaps setting an alpha < 1 there would make everything leave trails when moved. If you want trails only on some objects, that would be a bit more complicated.
Anti-Alias per object: Maybe there is an easier way, but antialias is set in context3d.setBackBuffer(). This is a global setting, but OpenGL like graphics pipelines usually change global settings before rendering an object so I guess you could change it per object on rendering. Perhaps this could be added as a property on renderable objects. Could you check if its there and if not we add it to the feature request list? hth!
