It would be very useful if we were able to set an order's Ship By Date when it is created via the Custom Store integration. Unfortunately, there is currently no available field for Ship By Date.
In our case, this means that for some stores (eBay, Amazon and our websites which use the full API connection) the Ship By Date is present but for stores which use the Custom Store approach this isn't possible.
Using automated rules to set the ship by dates doesn't work in our case, as it doesn't take into account weekends and bank holidays. Ideally, we would want to be able to set the Ship By Date to be "X number of business days after the order date". We don't ship on Sundays, so the current option to set "X calendar days after order date" isn't suitable.