The point is that the Church has no prayers for suicides but there are two examples of Russian elders giving counsel in this matter:
'There was an occasion during the life of the Optina Elder Leonid (Lev in the Great Schema), who died in 1841. The father of one of his disciples, Paul Tambovtsev, had died an unhappy and violent death by suicide. The loving son was deeply grieved by this and poured out his sorrow before the elder thus: "The hapless end of my father is a heavy cross for me. I am now upon a cross whose pain will accompany me to the grave. While imagining the terrible eternity of sinners, where there is no more repentance, I am tortured by the image of the eternal torments that await my father who died without repentance. Tell me, father, how I can console myself in this present grief?" The elder answered, "Entrust both yourself and your father's fate to the will of the Lord, which is all-wise, all powerful. Do not tempt the miracles of the All-high, but strive through humility to strengthen yourself within the bounds of tempered sorrow. Pray to the All-good Creator, thus fulfilling the duty of the love and obligation of a son." Question: "But how is one to pray for such persons?" Answer: "In the spirit of the virtuous and wise, thus: 'Seek out, O Lord, the perishing soul of my father: if it is possible, have mercy! Unfathomable are Thy judgements. Do not account my prayer as sin. But may Thy holy will be done!' Pray simply, without inquiring, entrusting your heart to the right hand of the All-high.'
'The Church does not command [us to pray for suicides]. How then dare its sons and daughters to pray [for them]? What is evident here is an attempt to show that we are more merciful than the Church, than God Himself. It is better to limit ourselves to feeling pity for them, entrusting them to the immortal compassion of God, and praying for them in our private prayers, that He deal with them according to His loving-kindness and according to your faith in that loving-kindness.' St. Theophan the Recluse.
Whilst St Theophan does not expressly say so, his counsel should, I think, be seen as like that of Elder Leonid, that is, for the consolation of a close relative of the suicide. I am sure that any person ought to seek the blessing of their spiritual father to say such a prayer and not presume to say pray so of his own will. As for a historical person such as Judas, I can see only danger in presuming to pray for his soul.