Thanks, very interesting. I just started to read more about Blender with the idea of looking for some exporting tools later.
May I ask why you decided to go for direct MDL export? I think the preferred way is to write the X file and let XtoMDL make the MDL file. This is also easier as XtoMDL can do a lot of optimizations for you.
And I agree with Bill on the MDL import functionality. That is something we should be really careful with (especially in loading it into a modelling tool), as it would allow people to steal and modify other peoples work a lot easier.
If the world should blow itself up, the last audible voice would be that of an expert saying it can't be done.