Defining an emacs minor mode
I think you did it the proper way.
Next would be to toggle your minor mode in your emacs configuration file .emacs.d/init.el with a hook probably like this :
(add-hook 'org-mode-hook 'komis-luna-minor-mode)

If you want your minor mode to be enable when entering org-mode.
For further and more specifics questions and problems, you should probably take this post to Emacs Stack Exchange.

Have coded an emacs minor mode with the definition shown below.
Would it be possible to simplify this, to perhaps call a function instead?  Or is it not such a big deal having a minor-mode defined in this way ?
What would be the general way to set a minor-mode in terms of functionality (e.g. enable, disable, ...) ?
(defcustom komis-luna-signal t
  "todo"
  :group 'komis-luna)

;;;###autoload
(define-minor-mode komis-luna-minor-mode
  "Uses large geometric shapes for displaying heading levels."
  nil nil nil

  (let*
      (($keyword
        `(("^\\*+ "
           (0 (let* ( ($kondor
                         (- (match-end 0) (match-beginning 0) 1))
                      ($inline-task
                         (and (boundp 'org-inlinetask-min-level)
                              (>= $kondor org-inlinetask-min-level))) )
                ;;--------------------------------------
                (compose-region (- (match-end 0) 2)
                                (- (match-end 0) 1)
                                (komis-luna-shape-select $kondor))
               ;;---------------------------------------
               (when $inline-task
                  (compose-region (- (match-end 0) 3)
                                  (- (match-end 0) 2)
                                  (komis-luna-shape-select $kondor)))
               ;;---------------------------------------
               (when (facep komis-luna-typeface)
                  (put-text-property
                     (- (match-end 0) (if $inline-task 3 2))
                     (- (match-end 0) 1)
                     'face komis-luna-typeface))
               ;;---------------------------------------
               (put-text-property
                  (match-beginning 0)
                  (- (match-end 0) 2)
                  'face (list :foreground
                        (face-attribute 'default :background)))
               ;;---------------------------------------
               (put-text-property (match-beginning 0)
                                  (match-end 0)
                                  'keymap komis-luna-mouse-sweep)
               ;;---------------------------------------
               nil )) ))))

    (if komis-luna-signal

        (progn
          (font-lock-add-keywords nil $keyword)
          (font-lock-fontify-buffer))

      (save-excursion
        (goto-char (point-min))
        (font-lock-remove-keywords nil $keyword)
        (while (re-search-forward "^\\*+ " nil t)
          (decompose-region (match-beginning 0) (match-end 0)) )
        (font-lock-fontify-buffer)) ) ))

