Render Hole-mesh on another mesh

I would like to render a hole onto a mesh without changing the geo of the mesh (it would mean to create a separate material and such)

Using Translucency + No Depth Test partly works, but as you can see, you shouldnt be able to see the lower parts of the mesh and it should be occluded by the original mesh.
Anyone knows some trickery to achieve this?

Cover the hole on top with a lump that renders custom stencil/depth. Only show decal fragment if it is behind the cover.

That might actually work! I’ll try that.