Slow down everyone. You are not thinking about RM in the right way. RM is not a precision tool you can use to craft an itinerary for any given day of the year. It is more of a big hammer approach which takes conservative guesses for line waits and then builds an itinerary that will will work 99+% of the time. If you can't run a Sunday itinerary just use Saturday. The idea with RM is not for it to say "July 17, 2012" at the top. It is to have an itinerary that is functional and works. If you have that then the rest does not matter.
I have corresponded with Mark Winters at RM over the years (the RM founder) and I can guess what is driving their decision to not offer Sunday plans. It is a gutsy and principaled choice on their part. Our society has gotten so used to 24/7 stores and services (
Walmart, etc.) and long hours and everything open on Sundays. Many (in fact most) other countries are not so commercially minded and still remember that reduced operating hours and closures on certain days have value to society and laborers.
I think some here are making a mountain out of a mole hill. I understand your frustration but I really think it is misplaced and you can safely just use a different day of the week and get an equally valid itinerary.
Hope that helps!