Nice question. Here's something generic you can try:
(defun no-mondays ()
(interactive)
(minibuffer-with-setup-hook
(lambda()
(insert "monday"))
(call-interactively 'query-replace)))
And here's a refactoring:
(defun with-initial-minibuffer (str fun)
`(lambda ()
(interactive)
(minibuffer-with-setup-hook
(lambda ()
(insert ,str))
(call-interactively ',fun))))
(defalias 'no-weekends
(with-initial-minibuffer
"\\(?:satur\\|sun\\)day"
'query-replace-regexp))