Maybe make each Anima Weapon's Anima form unique to themselves so Anima that have 2 items can have their two anima spirits with the design to match the weapons or sword/shield and the ones that have 1 item can have one anima spirit with a appearance that match the weapon.

We currently learn that the Anima's spirit itself is still developing so his or her final form has yet to be obtained and it is only in a pure energy form due to not fully manifested yet.