I wonder if hooking up with a popular rules set might also work, as a lot of people did with the "Friends of Gaslands" thing. The creators of Gaslands never put out their own line of cars, weapons, or terrain, but mini companies would work out a deal with them and could use the Gaslands name for their own minis, weapons, and terrain.
One of my favorite rules creators is Nordic Weasel Games, makers of Five Parsecs from Home (Sci-Fi), Five Leagues from the Borderlands (Fantasy), Five Men from Normandy (WWII), Chrome Hammer (Cyberpunk), Weasel-Tech (Mecha) and some others. They're all minis-agnostic, but I wonder if becoming the "Official Minis of Nordic Weasel" might work? Kinda like how Mountain Dew is the "official" drink of e-sports or Ford is the "official" truck of the Dallas Cowboys? Both Five Parsecs and Five Leagues have been picked up by Modiphius Games
Wargames Atlantic already has a ton of boxes that would work with Nordic Weasel's games; plenty of Sci-Fi and Fantasy, and historical that would work great with low and dark fantasy (my preferred brand of fantasy). Slapping a "Great with Five Parsecs/Leagues!" blurb on your boxes, and perhaps Modiphius adding a "Get your Five Parsecs minis from Wargames Atlantic!" could be great cross-promotion for both.
Edit: Then, again...I believe Death Fields is going to have its own rules set, so they might not want to explicitly promote those minis for a different game...












