The Source of Unity is Christ!
What is suppose to connect Believers in Christ together? Answer: His Life in us.
There is only One Body. Therefore, God only has one habitation. Yet, there are many members of this One Body. As we join ourselves to Him in truth and love then we are joined to others who honor and love Him, as well. True unity is not found in starting with each other but rather in starting with Him. There are many "bodies" of people that have so-called "unity", but if they are not lined up with the Lord Jesus in His purposes then they will not be "one" with He and His Father (John 17) and subsequently, other Believers who are also lined up with the Lord. You can sense this by the Spirit because you won't discern life (Jesus) and truth in that "body". Where Jesus is not the center and the focus of each individual, that particular "body" will not give off a "savor of life", and anything that is not of His life is death.
If the Spirit of God is absent, then it is just another religious tower of Babel. Where the spirit of the Lord is there is life. Uniformity exists today in many groups and "bodies", but that is not necessarily unity. As each individual aligns their heart up with Jesus, then they will recognize/discern others who have also been joined to the Lord in His purposes and will.
As the focus is not on you or I it is never on the Body as a whole, either, but on Jesus Christ (the Head). Never on us, always on Him. He must always remain the focus and the centrality of all things. There are many "groups" that major and focus on themselves and their collective unity and that is also a deception and not according to the Lord's prayer, "That they may be one as WE ARE ONE". What does that mean? Jesus brought His will into harmony with His Father's will. His Father's will became His will. "Not my will but Thine, be done". That is how we are one. Not by becoming one with each other, but by becoming one with Him. By becoming one with Him, we will be one with each other. We labor to enter His rest (harmony with His will), not each other's.
So, we are not to be conformed to men or be conformed by men. Many think that if they can conform others to a certain standard (their standard) then they will have achieved something on earth that is of God, but "unless the Lord builds the House, they that labor, labor in vain". The only acceptable "conforming" is to be conformed to the image of Christ by the inward work of the Holy Spirit. As each man yields to the Lord and allows His work to go on in his/her life, they will be a functioning and loving member of the Body and in complete unity with other members (who are also looking to and yielding themselves to the Lord).
We are not to be 1-dimensional, focused on the outward and not discerning what God may be doing in individual hearts. We build up individuals and leave it to God to position (fit) them in His Body. As we build up those whom the Lord brings to us then we are building up the Church. No need to conform anyone to our "vision" and the foundation we are called to build on is Christ.
1Co 3:10 ... But let every man take heed how he buildeth thereupon.
1Co 3:11 For other foundation can no man lay than that is laid, which is Jesus Christ.
Eph 4:15 But speaking the truth in love, may grow up into him in all things, which is the head, even Christ:
Eph_4:16 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.
Col 2:19 And not holding the Head, (that is the key) from which all the body by joints and bands having nourishment ministered, and knit together, increaseth with the increase of God.
As we hold the Head we will receive nourishment and are healthy (no gangrene) and our sinews and muscles and tendons will remain knit together, and the church will continue to grow strong and increase and this life is from the Lord.
The source of unity is not a shared vision or goal, a doctrine or creed, a man or men or a shared experience. The source of unity for Believers is a Person - Jesus Christ.
Only as each individual holds to the Head will they then be in unity and harmony with other members of the Body who are doing the same. It cannot happen the other way around.