The scripts that generate and read wikiversions.dat tolerate a wider range of syntactical quirks than are actually seen in the file. Additionally, the external version field may not be required at all any more.

Does anyone have a few cycles to spare to make the PHP implementation simpler, by dropping the third field, and making the file format be JSON?

It would be up to you whether to drop the field from the CDB file as well or whether to simply hard-code an empty value for it.

This would make it much easier for Bryan to have the Python implementation match PHP in behavior.