Guys, we've been there already, no need to reinvent the wheel.
The models were never designed as a solid object, taking advantage of specific Simplify3D slicing mode to allow designing internal trussing within a single pass shell. If the walls had thickness, it would be finite. This way we're able to decide, how many perimeters thick the walls will be. I admit it's kind of an intentional hack.
Imagine the internal trussing as the intersection between these cylinders. Initially, we took advantage of Simplify3D not joining the intersecting meshes along with variable settings across Z heights and promoted it as the go-to slicer for this task since 2015.
PrusaSlicer developers recently kindly implemented a new slicing mode called Even/Odd - it's the v4 behaviour shown in the picture above in my previous post to allow slicing of our models.
I'm pretty sure, we need the option to switch between v4 and v5 slicing modes, otherwise, Simplify3D won't support slicing our models anymore.
We were experimenting with flipping normals (top side of triangles) on some models, such as B-25 to allow slicing in PrusaSlicer before they provided the Even/Odd mode but it didn't provide any satisfactory results anyway. That's probably why you see some internal structures in some models but never all of them.