If only it were that easy.
Nevertheless, SSPX's sin of schism needs to be atoned for and reparated. They will do this in part by stopping their wholesale attacks against the Novus Ordo and by focusing themselves on preserving the Old Rite and by improving the New Rite without seeking to undermine or destroy it. The SSPX also should accept the full binding dogmatic authority of the Second Vatican Council an renounce all attempts to nuance, downgrade, subordinate, and/or diminish its Constitutions and Declarations through sophism and subterfuge. What is required of the SSPX is simple: that they embrace and love the Church NOW, and stop making an idol of an ideal Church of the past that frankly, never was.
Finally, regarding the defiant stance of Bp. Williamson, what he's really saying is that he is threatening to remain in schism even if the SSPX were to be reconciled with the Holy See. My take: so be it. He will then become an apostrophe to a footnote in the history of the Universal Church and only so much background noise. The choice before him is clear: assume a constructive posture, or become irrelevant. Now, let me bring to your attention this quote from Bishop Williamson:
Your Eminence, if ideas did not matter, you might be a good Catholic, but since the virtue of faith is seated in the mind and not in the heart, then so long as your mind swings between Tradition and modernity you are, despite yourself, in your position as Guardian of the Faith, a terrible enemy of the Catholic Church.When I accuse SSPX leaders of hubris, arrogance, and pedantery, this is exactly the kind of statements that I have in mind. This too requires repentance.
So, let us pray for reconciliation between the SSPX and the Holy See, that by rejoining the Mystical Body of Christ may the life of the Spirit once again course through them; may we all rejoice in the arrival of the prodigal son, for if one they were dead, then they will be alive again.