I don't believe that was the kind of "uniting" that was intended. We may try to all unite and the churches in the world have tried it before, but it is not really possible.There will be the false church that just tries to unite by man's efforts those who are not changed by regeneration of God's Spirit, and that's not what we want. But it's GOD who UNITES us BY HIS SPIRIT into the true body of Christ in the spiritual realm. That is the kind of uniting we need. His Spirit within us bares witness with the Lord's Spirit in others and we are united with them in the Spirit, not in the natural. That's the only way it will work.
Instead of saying 'Uniting all Christians as one body'
we could be 'Christians United By The Spirit Of God'
the problem with that is not the idea, but the simple fact that the only ones united by the holy spirit of God Himself are the saints... and we have no saints here, we are all sinners, so we are not united in one truth of God ,but divided by following sinners [or following scripture that disagrees with all the churches of modern christendom - since the saints are found here and there when Jesus takes them, 'from one end of the heaven to the other' ... they are not all together in this or that church of christendom, and they are few , not many , only some two thousand alive at any one time on average [since Jesus tells us there are but 144,000 for all the time between his first and second coming-Rev 7:3-8]
So the sinners will be united in belief [Rev 13:3-7] but in unism AGAINST the saints of God [Rev 13:8] ... that is the fate of all the word who are not baptised of the spirit, who are not baptised with 'fire' of trial of their faith in perfection OF LOVE ...
1 Peter 1:7 That the trial of your faith, being much more precious than of gold that perisheth, though it be tried with fire, might be found unto praise and honour and glory at the appearing of Jesus Christ:
Luke 3:16 John answered, saying unto them all, I indeed baptize you with water; but one mightier than I cometh, the latchet of whose shoes I am not worthy to unloose: he shall baptize you with the Holy Ghost and with fire:
Thus whilst you suggestion is wholly in line with scripture, this ain't an assembly of saints, but a divided gaggle of sinners who will only unite when Satan calls for unism in believing he is the god and saviour, the christ [annointed king] of this world of men...
Do not be sad about this, because it is just the next stage in God's plan to redeem all creation, both Satan and mankind hae to be humbled by making this colossal mistake about the power of God's truth to deat even Satan and a united mankind with a third of the angels alongside... it is rather God's way of showing the power of the truth about love, that it can defeat this asembly so very certainly and easily...
but there is much suffering because men followed unloving ways and choose the antichrist to worship, God has to allow men to sufer else men will not believe that this way is wrong....
So the evil on men of suffering is for good in the end, one can thus rely on the love of God for all, throughout this ordeal by 'fire' of ones faith [if one is given any true faith yet anyway]