Christ the King, a detail from the Ghent Altarpiece by Jan van Eyck.
The Latin antiphon is:
- O Rex Gentium, et desideratus earum,
- lapisque angularis, qui facis utraque unum:
- veni, et salva hominem,
- quem de limo formasti.
- O King of the nations, and their desire,
- the cornerstone making both one:
- Come and save the human race,
- which you fashioned from clay.
"He shall judge between the nations, and shall arbitrate for many peoples; they shall beat their swords into ploughshares, and their spears into pruning-hooks; nation shall not lift up sword against nation, neither shall they learn war anymore." Isaiah 2:4
If you are going to acknowledge Christ as King of the Nations, then using a prayer from one of them may not be a bad thing.
"May all beings everywhere plagued with sufferings of body and mind quickly be freed from their illnesses. May those frightened cease to be afraid, and may those bound be free. May the powerless find power, and may people think of befriending one another. May those who find themselves in trackless, fearful wildernesses - the children, the aged, the unprotected - be guarded by beneficent celestials, and may they swiftly attain Buddhahood." Buddhist prayer
I can reconcile this one with my faith as the "beneficent celestials" to me are "angels and archangels and the whole company of heaven" . As to "attaining Buddahood" - well, being perfected in Christ through his Incarnation, Death and Resurrection is achieving perfect fulfilment or Buddahood. If Christ is the Cornerstone, then he draws all nations and faith to himself and perfects in due course all our errors and misunderstandings. or Anonymous Christianity - the theological idea that declares that those who have never heard the Gospel might be saved.
You can find traces of this idea in the Vatican 2 document "Lumen Gentium", which states that those "who no fault of their own, do not know the Gospel of Christ or His Church, but who nevertheless seek God with a sincere heart, and moved by grace, try in their actions to do His will as they know it through the dictates of their conscience – those too may achieve eternal salvation". (LG para 15)
The German Jesuit theologian Karl Rahner's put it more forcefully: Non-Christians could have "in [their] basic orientation and fundamental decision, accepted the salvific grace of God, through Christ, although [they] may never have heard of the Christian revelation."
King of the nations, bring ALL your children into the fullness of life that is your will for us all. Amen.