Thats sounds like it could work, but which localisation patcher do you mean? The one I use does not have any tags in it. "FEATURE_BEAST", or TITAN, or DEMON, they are not in the list.
Ah, but the basic template.lng isn't the be-all-end-all of what you can change. Most of the stuff that was deemed irrrelevant for localization work has been culled from it. Use the string dump as your guide, as long as it is in the format "|old thing|new thing|" it should work. It's kind of astonishing how robust it is.
Two other examples about stuff that isn't there to begin with:
|[CE_PHYS_ATT_CHANGE:STRENGTH:300:1000:TOUGHNESS:300:1000:START:0]|[CE_PHYS_ATT_CHANGE:STRENGTH:120:300:TOUGHNESS:200:400:START:0]|This nerfs the strength upgrade of vanilla zombies considerably. It applies to both animated stuff and biome thralls. Since you can spawn both in the arena, I can also 100% confirm that it works.
|[CE:PERIODIC:MOON_PHASE:27:0]|[CE:PERIODIC:MOON_PHASE:27:13]|If I've understood interaction tokens right, this should extend the beastmode of randomly generated werecreatures by an extra two weeks. It's meant to help with the "I invaded the fort and oops I turned back into a peasant after throwing the first punch" problem.