One other thing that I want is that the region be highlighted if and
only if it is going to be the target of the next command I give,
because I like to look before I leap. It seems transient-mark-mode is
intended to give me this by adding the concept of active region and
highlighting the region when it is active. However, many commands act
on the region even if it is inactive. kill-region and
copy-region-as-kill are two such commands. I am sure there are many
more, because it is much easier to write:

(defun my-command (BEGIN END)
  (interactive "r")
  ;; do something between BEGIN and END
)

than:

(defun my-command (BEGIN END)
  (interactive (if (use-region-p)
                   (list (min (point) (mark)) (max (point) (mark)))
                 ;; figure out what to do when no region is active
                 ;; * act on the whole buffer
                 ;; * act on the current narrowing
                 ;; * signal an error
                 ;; * do something else sensible
                 (list ?? ??)))
  ;; do something between BEGIN and END
)