I've been working on removing redundant `function' around `lambda' in
Emacs core, so here is a patch which does the same for Org-mode.  Note
that Info node `(elisp) Anonymous Functions' says that:

     The read syntax ‘#'’ is a short-hand for using ‘function’.  The
  following forms are all equivalent:

       (lambda (x) (* x x))
       (function (lambda (x) (* x x)))
       #'(lambda (x) (* x x))

IOW, we can safely remove the wrapped `function' form.

Please see the attached.  (My copyright assignment is on file.)