I've recently updated the information page to better address issues like this, or at least to provide better context as to what is included by default, and what is left as optional.
To summarize, all optional planet mods fall into one of a few categories:
- Alternate Start (Lignumis is currently the only one that forces itself as an alternate start)
- Modifies Endgame (Nexus Extended and Shattered Planet both make changes to promethium processing and modify the "endgame" in different ways)
- WIP (includes newly released planets that plan to add more content, and older planets that are still receiving regular updates)
- Abandoned (planets that haven't received any updates in several months, or are otherwise lacking in content with no expected updates)
Erimos Prime probably falls somewhere in between WIP and Abandoned, since the last update was 4 months ago, and it has outstanding issues that need addressing (though seemingly nothing that would make it technically unplayable, like error on load or during runtime; only balancing issues).
Putting it bluntly; this planet mod is optional for a very good reason (and I might make it a hidden optional mod, if no updates are made in the next couple months). It already isn't even mentioned in the main info page (though that is more of an oversight than anything else)
Suffice to say, I won't be doing anything about 'fixing' Erimos Prime. I would simply advise against using it to begin with.
Oh, almost forgot to mention from a relatively recent report, but it is most likely incompatible with Lignumis, yet another reason to avoid it.