When they're not busy, I've seen the CMs at CS places go well above-and-beyond the call for us, even so far as researching information about ingredients used in their offerings, regarding our special dietary needs. Beyond that, as long as you're not asking them to adjust something that is substantially pre-made off-site, you should be relatively successful with such requests: Any "construction" related requests, for things they'll be making for you fresh, will almost surely be honored.