I don't think there is a flap over micaceous clay; in fact, if I were doing this commission, that is what I would use -- not heavily grogged terra cotta (regardless of the "dudes" endorsement). If you know what you are doing, making cookware is fine. Personally, unless I have made the form and was comfortable doing so, I would be inclined to pass the commission. Don't have enough insurance if things go bad on someone's stovetop or in their microwave.
Here is clip from an old Clayart discussion, from Vince Pitelka:
"The outgassing of toxic volatiles can continue throughout the firing, so ventilation should continue as long as the kiln is firing. At low temperatures you have sulfur dioxide, and at higher temperatures you have zinc and possibly fluorine, lead (if any was present), and other materials. Once the kiln has shut off there is no toxic danger at all."
I usually get the sulfur burn-off around 800 to 1000F, especially for bisque fires. You will also get burn-off during glaze firings all through the firing cycle, wax at lower temps, glaze materials at higher temps. My kiln vents to the outside (it is an L&L), but I'm often not able to work in the studio when it is firing. That is one reason I tend to fire overnight.