Ok, here's a thought... I don't know how to make it a plugin, maybe somebody smarter could do that, but you could hack the function... the wp_register function shows either the register button or the site admin button depending upon if it's a logged in registered user. So you could change the function to point to the post page instead of the dashboard.
In wp-includes/template-functions-general.php find wp_register. Then change
$link = $before . '<a href="' . get_settings('siteurl') . '/wp-admin/">' . __('Site Admin') . '</a>' . $after;
To say:
$link = $before . '<a href="' . get_settings('siteurl') . '/wp-admin/post.php">' . __('Make a New Post') . '</a>' . $after;
I tried just adding the second line to see if it would show both, but that didn't work. Maybe it's just missing something to make it do that.