The thing is...
You don't really need to go to the MMA at all. The codes to achieve the control are already in place. Simple program changes are all that is necessary on a defined MIDI channel. In fact, Roland already have most of the needed commands in their specs. Korg have most of the commands in their specs. The trouble is, they are not standardized
So, you can control a Roland arranger with a Roland arranger, and a Korg with a Korg, but you can't control a Korg with a Roland (or vice versa). And, as far as Yamaha go, you can't control them as slave, or use them as a master
Most of the functions to control an arranger are simple buttons. Push this, get that... So program changes to do fill selection, variation change, breaks, Intros, endings, etc. are simple commands. Roland specify a particular channel as 'control' channel, and then PC#'s trigger the arranger functions. Other CC00/32/PC#'s can select the styles.
So, instead of getting the MMA (who take forever to get anything done) involved, it is a case of trying to get basically the Big 3 (everyone else will follow if just two or three standardize - remember how few embraced MIDI at first) to standardize the codes to do this. We don't need new codes. We just need an agreement about which current ones to use.
For anyone that is interested, I might suggest looking at a Roland 'Parameter Reference' .pdf
http://roland-arranger.com/index.php?option=com_remository&Itemid=64&func=fileinfo&id=35 is the G70 one. It shows (p.17-18) what can be done, from the style division #'s, to the UPG (registration) codes, and the Style and Custom (user) style addresses...
It's fairly comprehensive, but the only problem is they are not changeable. Likewise for Korg (I don't know their manuals!). Given Roland's comprehensiveness, and also their part in the original GM/GS patch standardization, it might be expedient to ask the other manufacturers to comply with these already established standards.
It remains to be seen if there is any interest from the manufacturers, but, were I them, I would be looking at this as a way to sell more arrangers. If you can hook them together, many WILL buy more than just one!
Let's see if they are listening. These are strictly OS changes, no extra hardware required, and, other than Yamaha, are already sort of in place. Just the standardization is all we need...
Who is interested in this? I know for a FACT that if I could control an S900 with my G70, I would already have one, maybe even a T2. So, come on Yamaha... get crackin'!