Ian,
It's not my job to convince you or anyone else what can or can't be done with my arranger. I merely pointed out factual information based upon what it can and will do. .
Why am I not surprised you wouldn't back up your claims?
Yamaha, Korg, Roland and Ketron have done it. I have posted my work here several times.
Talk is cheap, I suppose.
It appears you had to add a lot of extras...I haven't needed to add anything to my Tyros4 to make it fit my needs (other than re-program some styles, which was accomplished on the instrument), and I'm a professional player, working in the business over 40 years.
Enjoy whatever it is you play.
Ian
PS... If I upgraded every 3-4 years or so, the cost was very little, and I made that back with just a few gigs.