Don, I have to say I'm not convinced by the "trespasses" theory you have put forward. Even in modern usage, the word has many meanings besides the legal one of trespass on land, even if that is its most common usage.

My history is a bit rusty, but my recollection is that trespass and poaching became a big issue after the 18th century enclosures, not the Tudor ones, which were far less widespread and caused less disruption to the rural way of life.

To my mind the theory that the word was put in by landowners to keep the peasants off their land is undermined by the following phrase in the Lord's Prayer, "as we forgive those who trespass against us".

The Book of Common Prayer was intended to be an inspirational text in a language which was itself undergoing a rapid and creative development, rather than an academic translation. It drew not only on early texts but on more recent translations. In the Authorised Version, the text varies between the Gospels. To my mind, "trespasses" in its meaning of "offences" is a much broader and more inclusive word than "debts". As a piece of literary writing, it gives the phrases rhythm and metre, which "debts" or "sins" lacks. I'm sure these are the reasons it was chosen for the BCP.