Hm, yeah there are many things a gameplay mod could do that would short-circuit what this mod does. This mod removes DoomWeapons, any DECORATE stuff that extends from Weapon instead of DoomWeapon would make it through. Likewise the monsters auto-kill zscript checks for typical Doom monster states like See, Missile, Melee, and Heal; if a custom monster uses states besides that it would remain alive (but invisible) during gameplay and some of its sounds might play.
I wrote Tourism Deluxe mainly for exploring maps with vanilla Doom gameplay. It's possible there are smarter, more thorough ways I could deactivate/hide non-vanilla monsters and weapons, I'll investigate a bit.