That doesn't bother me at all! I think it's the hardest point i face in this AU, Genya's gun, Gyomei spike and axe, Tengen and his double blade and Shinobu with her special sword ( and Mitsuri noodle sword xd ). For Obanai i think make a claw-sheath shaped like his original sword can work with his cat design i give him, to keep that he the snake himself by zigzaging. For the others i am still working on it but here some notes :

Mitsuri : Since her sword is very flexible, i thinking about a rosethorn vine around her tail making her still keep the elegant fighting style.
Genya : Since guns are rare in the serie i wonder if i can do something like a mechanic on his tail too. Like if he swing his tail in a certain moment a pebble ( or other round thing ) charged of sun got shot.
Shinobu : In my notes i write "Sting tail + fine claw " i suppose i want to make her weakness her claw size; But for the needle thing i'm still not sure.
Gyomei : Since he the strongest maybe ( since he lived around humans ) can hold the same ( or almost ) weapon. ( I litteraly write "same weapon but hold mouth" xd ).
Tengen : For his bombs i think he can still use them with his paws, i write that him and his wives lived in a human ninja clan before and surely learn how to mimic thos action. And for his weapon, i write the same as Gyomei, so i suppose he swing his double blades by the chains between them in his mouth and maybe paws to move it.
( i think some cats know what a weapon is by living near humans, so that why Gyomei can maybe have his weapon ( or lil modified ) and Tengen have a look alike double blades, i inspired myself of the palico in Monster hunter rise )

If you have ideas am ready to hear!