After reading your reply, I realized I made a mistake in describing the new ability. I do not mean "send letter" as in email. On the contrary, I meant printing a hard copy. The ability is quite the same as printing a PO. Rather than printing a PO, I want to print a letter. I run a kindergarten. After a prospect parent has registered their child, I'll convert prospect to customer. After which, I'll send the parent an enrollment confirmation letter (via snail mail). Since their address and contact info is readily available in xTuple, it should be quite simple, in my opinion. The enrollment confirmation letter is always the same and can be made into a template where in only the address and contact info is a variable. This new ability perhaps can be included under CRM > Accounts. It is also can be a To-do item to "print enrollment confirmation letter", for example.
I hope is it clearer now.