Pickysaurus is working on getting mod managers to validate the FOMOD schema so that fewer authors will publish broken ones. See this modding.wiki page for more information.

The main problem appears to be that there is no stdlib way to do this: https://stackoverflow.com/questions/299588/validating-with-an-xml-schema-in-python
So we'd have to add lxml as a dependency. Which may make this a no-go - @Utumno?
Edit: actually, pyxb may work as well, which would allow us to generate schema bindings AOT if I understand it correctly, so no new dependencies.
Edit 2: another option may be making lxml an optional dependency, which would mean you don't get the validation if you don't have it installed. Depends on how similar the API is to stdlib.

Ganda's repo with the schema can be found here: https://github.com/GandaG/fomod-schema