Like the title says, I'm in need of some kind of modifier (since I'm doing a non-destructive workflow in order to parameterize a lot of things -- for the context, I'm creating a base for a modular tileset) that acts like the boolean modifier set to difference, but I want it to leave subtract (cut off along the volume border similar to a knife and delete all vertices within the volume). The reason for this is that I've got the tileset planned so that things will line up with pieces from neighbouring tiles, so the the final compositions will always be complete volumes, just not the pieces. But since the pieces end up as complete volumes if I use the current boolean operator, it causes the shading to get fucked up along the seams between tiles due to them having faces along the borders (not to mention that it results in a lot of redundant geometry that will never be seen). Any suggestions as to how I can accomplish this non-destructively?
You could add a Solidify Modifier before the Boolean. Also, add a Weld Modifier after the Boolean.
Use a very small Thickness in the Solidify and make sure the Distance in the Weld is high enough, so that the newly created vertices from the Solidify get welded back together.
Regarding the Shading: That should go away if you enable Auto Smooth.