TG, after giving a kazillion tickle sessions to my lady friend I've learned one thing... the feet don't really do it for me like they used to anymore! My focus now covers much more ground than just the feet, so to speak. Sure, I'm still a fan of those five-toed delights, but I've found that I've become much more interested in tickling the nape of the neck and the back, the tummy, the legs and, well, you're familiar with a woman's anatomy, I'm sure. I'm sure once your friend has access to more than just the feet, he'll realize what a medley of ticklish delights he can find in you! But don't give him access to more than you can bare, so to speak.
By the way, is it the hard tickling that makes you dislike foot tickling or do you think you can stand gentle, soft caresses? Or are you just grossed out by feet in general? I've turned many a woman around on the topic simply by handling their feet in a much more delicate, gentle fashion. I'm asking this just in case your friend insists on focusing on your feet and only your feet.