Date Format And Calendar Start Date in Sell

We as a business start the week on a Sunday and work with a date format of DD/MM/YY, however the system will only allow us to have one or the other of these settings active.

If I change between 12 and 24 hour format this changes these setting of both of these so I cannot have the week start on a Sunday with the date format required.

It would be great if these settings could be adjusted separately within the system so we can choose to have both or neither.