It would be cool if we had sporadic blight portals that would spawn at various locations throughout Doom that would allow mobs to come in. It would be like a blight anchor sort of but, you wouldn't be able to target the portal itself. It would just let mobs in for 10 minutes or so and spawn once an hour possibly at multiple locations.
There would be no safe place in Doom just to hang out. This same idea would also work well in all the Deadlands.
-Kor