Regarding the filioque: Fr Paul Evdokimov has suggested adding a spiritusque to the western creed:
To render the western conception of the Filioque as acceptable as possible to the Orthodox, we can say that the Father gives to the Son the energy of spiration, not of origin but of manifestation. But in this case, the perfect balance of the Trinity requires that the Father gives to the Holy Ghost the energy of paternity, which equally is not of origin but of manifestation.
The Holy Ghost is breathed by the Father (origin) for, in, with, through, and by the Son (manifestation); and this dyad entails another, corresponding one: the Son is begotten by the Father (origin) for, in, with, through, and by the Holy Ghost (manifestation). Ek tou Patros dia tou Huiou corresponds to ek tou Patros dia tou Pneumatos.
The Filioque, purely manifestation, is balanced by the Spiritusque, equally purely manifestation. This balance would improve the Nicene Creed, in which the divinity of the Holy Ghost is not sufficiently explicit.