Alex and Scottyee,
I have a good friend that has two PSR-9000 pros and he wouldn't part with them for love nor money. He absolutely must have 76 notes....probably because he is first and foremost a piano player.
I came from the Hammond B3 to the Yamaha Electone (even took the Electone music program and ended up teaching it after graduation) so I'm used to playing chords in a way that's pretty close to what's needed on a 61-note arranger.
Just because Tyros 1/2 isn't a "pro" instrument doesn't keep a professional entertainer from using it to make terrific music with it,as Scottyee has expressed.And Gary(travlin'easy) makes the most of the 3k which is not truly a "pro" instrument....he's making a living!

Professionals have always been resourceful and make the most out of a instrument...sometimes even using it's limitations to their own advantage.
The arranger module is a great idea...I used Roland's great series of RA arrangers,the last one being the RA-90,but again they were dropped for some reason after the RA-95(correct me if I'm wrong).My understanding is that they were hard to sell because they were too pricey....
A "Tyros in a Box"....that would be ideal, and something I'd love to have, but Alex, I'm afraid you are right about Yamaha's disinterest in making a module.
I have used an 88 note controller connected to the 3k but it was off to the right (in an "L" configuration) and I used it only as a solo piano and sometimes to play along with a midi I had previously recorded.To have the 3k mounted above the controller would have made both difficult to use.
The inside info I have received from other Yamaha Clinicians is that a 76 key Tyros 2 is not in the near future....a boon to Korg and Roland and others...but a bane to us Yamaha devotees.
Ian