possible from python, but it's still work in progress. Pointers and collections are restricted to types derived from IDPropertyGroup (same as for operators), because RNA knows how to allocate/deallocate those. Collections have .add() and .remove(number) functions that can be used. The remove function should be fixed to take an other argument than a number. With the IDPropertyGroup restriction, pointers are more like nested structs. They don't have add(), remove() yet, not sure where to put them. Currently the pointer / nested struct is automatically allocated in the get() function, this needs to be fixed, rule is that RNA get() will not change any data for thread safety. Also, it is only possible to add properties to structs after they have been registered, which needs to be improved as well. Example code: http://www.pasteall.org/7201/python