My intention with this question was to take the "long view" and not necessarily consider what we have right now but where we want to head towards in the future. Converters are easy to write.
I like the idea of keeping the DAT syntax as it is right now and adding all the non-geometry stuff (i.e. normals, textures, etc) into a wrapper file. This will not break backwards compatibility as the existing software doesn't know about that stuff anyway. As long as a DAT file exists for every part and we don't define any part geometry stuff in the wrapper file then we don't need to worry about old software.
I like the idea of keeping the DAT syntax as it is right now and adding all the non-geometry stuff (i.e. normals, textures, etc) into a wrapper file. This will not break backwards compatibility as the existing software doesn't know about that stuff anyway. As long as a DAT file exists for every part and we don't define any part geometry stuff in the wrapper file then we don't need to worry about old software.