;; Make `kill-process' a command.
;; (put 'kill-process 'interactive-form '(interactive))
(put 'kill-process 'interactive-form
     '(interactive (kill-process-read-arg)))

(defun kill-process-read-arg ()
  "Obtain arguments interactively for `kill-process'."
  ;; Currently supports only the PROCESS argument.
  ;; Must either return a list containing a process, or signal an error.
  ;; (Returning `nil' would mean the current buffer's process.)
  (unless (fboundp 'process-list)
    (error "Asynchronous subprocesses are not supported on this system"))
  ;; Local function to return cons of a complete-able name, and the
  ;; associated process object, for use with `completing-read'.
  (cl-flet ((procitem
             (p) (when (process-live-p p)
                   (let ((pid (process-id p))
                         (procname (process-name p))
                         (procbuf (process-buffer p)))
                     (and (eq (process-type p) 'real)
                          (cons (if procbuf
                                    (format "%s (%s) in buffer %s"
                                            procname pid
                                            (buffer-name procbuf))
                                  (format "%s (%s)" procname pid))
                                p))))))
    ;; Perform `completing-read' for a process.
    (let* ((currproc (get-buffer-process (current-buffer)))
           (proclist (or (process-list) (error "No processes found")))
           (collection (delq nil (mapcar #'procitem proclist)))
           (selection (completing-read
                       (if (and currproc (eq (process-type currproc) 'real))
                           (format "Kill process? (default %S (%s)): "
                                   currproc (process-id currproc))
                         "Kill process: ")
                       collection nil :require-match nil nil
                       (car (cl-find currproc collection :key #'cdr))))
           (process (and selection
                         (cdr (assoc selection collection)))))
      (unless process
        (error "No process selected"))
      ;; Return list of arguments for `kill-process'.
      (if (y-or-n-p (format "Kill %S? " process))
          (list process)
        (error "Process not killed")))))