I might suggest some sort of claw, fortified body, night eyes gene's if you decide to add some more genetics down the line. I feel like they'd fit their xenotype.

I think that because the backstory of the Filox has to do with genetics and faith in the eldritch you could some unique genetic mutations similar to "More than ashes V2" and maybe also if it's possible they can receive blessings from the eldritch which mutates them further adding limbs and weapons and armors like how in Warhammer 40k those who worship chaos can become more powerful through mutations but I think it would suit them because the end game for Feral's are also becoming like huge mutants. They could add have unique characters in the game when raiding 1 pawn enters with a health trait "blessed by Cthulhu" or "Cursed by Cthulhu" and they much stronger then the rest of the Filox those who are cursed have like negative 50 mood debuff and are enslaved to do the will of their God and are fully mutated those who are blessed have a special weapon and maybe armor also but will have bonuses and have 1 unique blessing which mutates them in specific way making them look unique as leaders of the filox new colour or something. and maybe if the filox have more technological ages in tech have like shadows or assassins of filox which are like their special forces.

buff them.
they have thrumbo genes.
at least make them smart.

also, maybe give them their own animals and plants

while it's safe to assume they eat nutrifungis, what about a new type of drug plant, like gives them temp healing and combat buffs to help them deal with insects, or some new fabric plants that only grow in the dark, or special filox clothing, or give them filox specific crabs or insects for mounts or swarm animals, to help deal with insects

or just give them elder filox that are respected in their community for worshiping rngjesus or some crap like killing a lot

or maybe give them their own special psycast-Esq thing that uses aterium or some sort of filox machine that fuses them with aterium to become massive tanks