I am puzzled why no extension has been made for the IOIO boards.
You could be the first one making that.
People don’t just go around making extensions willy-nilly. Most extensions are made because people request them. This may possibly be the first time anyone has requested one for an IOIO device, whatever it is. I searched “IOIO” and this is the only topic that comes up in this forum.
Perhaps you should state how much you are willing to pay for it and detail what you need, that way if someone is interested they may develop one.