There are already a tool like this and you cud find in download, but it s on store. But that tool is totally limited and not a MDL expoter!

So I wonder If you are a mel scripter or a plugin developer. Because the problem is not writing out a WMP, but a batch export of mdl from Maya, so we need an exporter first. And after expoter comes out, it will not take much time for a Maya 2 3DGS tool.