I'm not a modder, but was sad to see The Two Sides shut down. Anyway, I am pretty sure this should work:
- Openly make a mod where all the sprites and text is contained in separate files, called "Invasion of the Bug Men" or "Angry Guys from Outer Space"
- Someone unknown to the modding team happens to spread a link to a complete graphics and text replacement which you simply unpack in the mod directory to overwrite the files
A company has to protect their intellectual property, so they are to some extent forced to send cease and desist letters even if they don't want to. In this way they wouldn't have to, only to those who hosted the entire integrated project or the imitation graphics. Would probably make game companies very skeptical towards any participants, but hey.