It looks like somebody has been working on recreating the VRC7 in an FPGA? I provided the link, for what it's worth; I don't know VHDL, so I'm not sure if this helps us at all, or if the PowerPak even has enough logic gates. But this forum is the place I should go to learn more about NES hardware, isn't it?
http://crystal.freespace.jp/pgate1/nes/ ... vm2413.htm
(sorry I can't provide a translation)
http://crystal.freespace.jp/pgate1/nes/ ... vm2413.htm
(sorry I can't provide a translation)