'That's the only constructive thing I CAN do... I certainly can't make one And I HAVE contacted Yamaha directly.'

No it isnt !!

You believe that you can propose a commercial reason for yamaha to make a true 76 arranger ? Then give them the numbers of additional tyros/psr buyers who would do so without eating into their eisting offerings or even if they did could make greater profit than they do now .

Garner all the support you can. You can start a petition right here and then on the yamaha, roland korg and ketron forums. You will meet some opposition ,sure as many of those individuals would never buy a yamaha no matter the number of keys and sure, many existing yamaha owners already love their 61 key instrument as you have already seen here and dont have the need or desire to buy a 76 key instrument. But dont let that stop you ! This seems like sucj=h an important issue to you i dont understand why you havent taken these steps already.

Stop theorising and get some hard numbers to support your argument and then maybe yamaha will listen. But if they say NO then you will have at least given it a genuine go and not just wasted thousands of words and time here talking to the WRONG people.

If you cant get say 200-500 interested people to even register that they wouild buy the product then dont be surprised if the answer is no. But give it ago. This is an itch that it would seem must be scratched for you and who knows, maybe many others.