Ban zombified Piglins to spawn on Overworld blocks

I replaced netherrack with cobblestone around my Nether portal incase Ghasts decide to shoot fireballs on me (cobblestone is blast resistant). So I have island of safespace inside Nether which I call my Base. I surround it with cobblestone whall aswell. 

And it is very annoying to return to my Nether base from a long trip and find hordes of z-plugins inside my fence perimeter chilling on that cobblestone blocks. 

I would ask to restrict piglins spawn on those blocks which are not originally from Nether (any sort of block from Overworld)

P.S. I also build roads and bridges in Nether to connect portals across my World and to cross lava oceans. I build them of cobblestone (to protect from Ghasts blasts and fall to lava). And those z-piglins are always on my whay!