I know of engineering firms who charge an arm and a leg to consult on this kind of thing. I'm not sure how much help you can expect from the arduino forums, as it is definitely leaving the DIY space and going into commercial business.
Off hand question, if you use an open source design in your system than has been certified by the FCC (but not by your company), does the certification carry over? I assume not, since that would make less money, though I guess it depends on the licensing arrangement.