This all sounds good. Sounds reasonable. Appeals to sensibilities that can not accept a gospel that requires anything of us. The problem is that the gospel does require things of us. Your position is simply opposed to almost everything the inspired scriptures teach us about salvation. Nowhere in Holy Writ is baptism described as a “witness to the person concerned” or as an “outward expression of an inward grace”. It’s just not there.
You've just said that the Gospel requires things from us; one of those responses is baptism. By undergoing it, we DO show that we have experienced new life.
I am not for one minute saying that baptism is unimportant, or an optional extra. I was baptised by immersion while at college - to the disgust of my parents and vicar who argued that my infant baptism was enough. It was a great occasion and a witness to many - I'm not sorry that I did it.
What I AM arguing against is the idea that a non Christian could repent, come to Christ, be born again and receive his Holy Spirit, yet, should he die before water baptism can be asked for or arranged, he wouldn't be saved. That when he met God after death, God would still judge and condemn him for not living long enough to be baptised.
The implication is also that babies, or children, who die before they could be baptised, would experience the same fate - condemned to eternal death for not going through the waters of baptism.
I disagree with that sentiment; Jesus said that whoever believed in him had eternal life, John 3:16, John 3:36, John 5:24, John 6:40, John 10:10, 1 John 5:12 - and whoever eats his flesh and drinks his blood has eternal life, John 6:51-54. Jesus is enough; Jesus is everything and is always enough for all of us. He does not need anything, or anyone, else to help him save us and reconcile us to God; he, alone, did that on the cross.