You said, 'Jesus says all things are possible with God, so no one can say this is impossible.'
Ray is saying, 'God only does those things that are in agreement with Divine nature. These include things like His love, infinity, justice, mercy, judgment, holiness and so on.
The Lord cannot sin and neither can He nor does He want to send certain sinners to Hell. He opens His arms of love to every human being. [John 3:16]
I believe in John seventeen Jesus is saying that He knows who are His people and implies that they are found in all denominations, and, of course, within the Catholic church. God is not urging a one world, universal church under one denominational banner. Each of us knows whether we are a child of God or not part of His church/kingdom. And we sense even on the board that most a part of the family of God and that we are bound together by His precious Holy Spirit. This is the Catholicity and universality that Jesus is referring to in His Word.
We are one in the Spirit we are one in the Lord.