Adding onto this…
The value should be able to go into the negatives so that things like a 3d effect could be executed e.g: doors and the sides of them, and perhaps even giving detailed arms a 3d effect if someone is skilled enough to know what they’re doing.

Another idea I had was for a sophisticated outline effect to be created. There can be a toggle that makes the outline layered behind the figure furthest back if the figure with the outline is joined to another figure, potentially also having an outline. This would allow more detailed figures with several parts t9 be able to keep their outlines without it looking weird. These outlines could be coloured, thickened, or even blurred, kinda like a drop shadow 2.0. If we wanted to get even crazier, we could have the outline appear hollow when the opacity is lower than one.