As far as I know, Nauticam does not have a plan for a flat wide port, but, one nice thing is that with the range of port adapters we have, you can use one of the existing flat ports (i.e. S&S, Seatool) that might work. Right now none of the 17-70's are on our port charts... which one are you planning on using? What diopter are you planning to use? Are you set on using this in a flat port - would you consider a dome?
I was hoping to use this lens as a substitute for both my Canon 60mm Macro and my Canon 18-55, but I do own and want to use a Subsee 10X with the sigma, so a dome port is not going to work.