While I'm aware of the many problems with accesskeys, they are already used
(some would say controversially) in the TinyMCE component. I believe that
one aspect which the dashboard evades is keyboard navigation. The AJAX bits
makes matters even worse, e.g. tabbing.
If accesskeys have already been embraced, why not underline letters and
assign accelerators to top menus (and sub-menus) on the fly, depending on
the platform and browser used? This functionality can be disabled when
editing in WYSIWYG mode. Think of editing comments by simply hitting
CTRL+M, CTRL+C. It doesn't/shouldn't lead to any user confusion.