Shinmera's Trial game engine, used in Kandria (which you can find on Steam), uses bits of the same machinery to implement the resourc system inside the game.
IIRC it has separate classes for "unloaded entity" and classes for various types of resources, and the protocol (think interface) for them includes the generic function that loads them into memory. The implementation of said function for unloaded objects uses CHANGE-CLASS method redefine the instance in place - meaning all direct memory pointers to the class are still valid and you don't need to use extra layer of indirection.
IIRC it has separate classes for "unloaded entity" and classes for various types of resources, and the protocol (think interface) for them includes the generic function that loads them into memory. The implementation of said function for unloaded objects uses CHANGE-CLASS method redefine the instance in place - meaning all direct memory pointers to the class are still valid and you don't need to use extra layer of indirection.