I haven't messed with Feral-Heart models and such for a while, and I've tried this before, but I've never liked trying to get models and meshes to work. I'm doing good to get blender open. However, I've wondered if it's possible to take a model of a map or area, convert it into a mesh, and use it as a map?
It's a bit hard to explain but let's say you wanted... Snowdin from Undertale, or The Glen from OneShot, to be a map in Feral-Heart. Find a (for these two examples, a 3D fanmade) model of the area, and then convert it and use it as a mesh for the entire/most of the map.
If collisions didn't work, you could put in invisible floors and walls, so that'd be the least of concerns.
Sorry if this isn't really in the right section. It's more of a "can you do it" than a "my game broke" kinda thing, but I thank you for reading despite this.
If it's possible, a picture or even video tutorial for someone who has problems with this kinda thing would be appreciated.