Steve,
Thank you enormously for your concern and your response to this problem, probably the only gripe past PSR2000/2100/740 owners have about this amazing keyboard.
On future models, the only real solution is to have dedicated buttons for the most commonly used functions - like TALK ON/OFF, HARMONIZER ON/OFF, ECHO/HARMONY ON/OFF, and EFFECTS ON/OFF.
As far as OS updates, I think that your idea is excellent.
I have another good idea. When the bottom of the LCD is set to BALANCE, button #8 is not being used. That button could be dedicated to TALK ON/OFF. I think the TALK ON/OFF is the most glaring button absent, because it makes it difficult to insert a stray remark into one's performance.
Let's say I'm performing for a dance, and a couple is doing a marvelous job, I love to be able to press the TALK button in the middle of the song and say, "Let's give a hand for the dancers." There are many other situations, where it is essential to be able to quickly get rid of that reverb to say something.
So I see your solution as the best. Assigning button #8 to one of the desired functions is second best. Enabling the keyboard to receive sysex or other midi messages to get these functions to kick in is also a good solution.
Whether or not I buy the successor to the PSR3000 in a year or year and a half, will depend a lot on whether this issue is resolved.
Thank you again, and Happy New Year.
Beakybird