Taking into consideration things JCL has mentioned before, like seperating the engine, renderer, and scripting into seperate pieces, make it more feasable down the road to offer more x-platform possiblities. If the same thing was done for other pieces like audio, then using OpenAL instead of DirectSound would be a possiblity as well. Same with OpenGL as a renderer.

With regards to formats, I know first hand the the code to do this is not quite portable. The reason for it is that the structs have padding in them that is written out to the files, and this means they are doing serialization by simply writing out the struct directly from memory. This wont work on other platforms since things like structure alignment and byte order may be different.