I think the hesitation may be that folks are reluctant to give you an answer you're not likely to appreciate: if you want to cover that coping in a seamless fashion, you're basically going to have to remove your entire deck, add new higher supports, and the replace the deck and fence.

I'm not a skilled carpenter myself, so I can't really tell you how best to do it. I will caution you that you probably do not want treated wood edges where the coping is now: it might be fine for a year, but after it weathers, it will provide your guests with 'thread-picked' swimsuits and butt splinters.