Since the xml files of mods tend to get pretty complicated and typos are hard to stop, I started working on a small tool to find those quicker.
It currently validates all files according to the schematas as well as checking Properties used by Modifiers for existance.

I hope it helps someone besides myself: https://github.com/Idrinth-s-Endless-Space-2-Mods/modvalidator/releases/latest