one-by-one mm-inline-text-html-with-w3m-keymap bindings

[jidanni@xxxxxxxxxxx]

In (emacs-w3m)Gnus Info we see:
     If you don't need to use emacs-w3m keys in article buffers, add the
     following line too:
          (setq mm-inline-text-html-with-w3m-keymap nil)

But it doesn't mention what if one _only wants to do_ what is on
(emacs-w3m)Key Binding Info:
   To change the key binding one by one, modify the `w3m-mode-map'
   variable in your `~/.emacs-w3m.el' file like the following:
     (define-key w3m-mode-map [up] 'previous-line)
     (define-key w3m-mode-map [down] 'next-line)
     (define-key w3m-mode-map [left] 'backward-char)
     (define-key w3m-mode-map [right] 'forward-char)

One can't just stick that in .gnus.el without causing errors.
There is also no guarantee that I will have done M-x w3m before M-x gnus.
Now what? 怎麼辦？