I wish to show that modes and forms are unimportant." He would be in danger of contempt of court.

If so small a departure from the mode of swearing would not be allowed, much less would he be permitted to kneel, or to lie on his face, unless he were some devotee.
No; there is a prescribed form, and he must yield to it.

It is also said, that, if there were cases in the New Testament in which it were doubtful, at least, whether immersion were not practised, we might argue in favor of mixed modes.

But immersion is baptism, in my view, because a person who is immersed is sure to get affused; and, affusion with water is all of the baptism which seems to me essential.

Leaving those who first departed from the apostolic mode of baptism by sprinkling, to answer for themselves, no one, of course, will deny that those who conscientiously think that they ought to be baptized by immersion, are acceptable with God, as well as others who are of a contrary persuasion.
Paul speaks of "divers baptisms." There began to be such in his day.