That is NOT mixing metaphors but multiplying metaphors. God has every right to apply a hundred metaphors if He so chooses. Paul says about the Bride/Wife of Christ that *this is a Great Mystery*. And so it is to some Christians (including yourself). Eve was a type of the Church -- the two shall be one flesh -- and that is the allusion to the Wife of Christ in Ephesians.
*The Body of Christ* indicates the fulness of Christ: And hath put all things under his feet, and gave him to be the head over all things to the church, which is his body, the fulness of him that filleth all in all. (Eph 1:22,23) Agree
*The Bride/Wife of Christ* indicates union with Christ: For we are members of his body, of his flesh, and of his bones. For this cause shall a man leave his father and mother, and shall be joined unto his wife, and they two shall be one flesh. This is a great mystery: but I speak concerning Christ and the church (Eph 5:30-32)
*The Building of Christ* indicates maturity in Christ: Now therefore ye are no more strangers and foreigners, but fellowcitizens with the saints, and of the household of God; And are built upon the foundation of the apostles and prophets, Jesus Christ himself being the chief corner stone; In whom all the building fitly framed together groweth unto an holy temple in the Lord: In whom ye also are builded together for an habitation of God through the Spirit... Till we all come in the unity of the faith, (this is the ultimate goal that the marriage metaphors speak of) and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ:.. But speaking the truth in love, may grow up into him in all things, which is the head, even Christ: From whom the whole body fitly joined together and compacted by that which every joint supplieth, according to the effectual working in the measure of every part, maketh increase of the body unto the edifying of itself in love. (This what one flesh means, no marriage necessary) (Eph 2:19-22;4:13,15,16).