A year without answer. Wow. I suppose I should look for another forum where someone actually listens. 

I notice the latest Aria Player/Engine update has a VST3 component.

Do you have plans to make a multi-channel output version of this VST3 plug-in?

MM Support says this is a matter for Plogue (maker of the Aria Player) to take up. Anyone have a Plogue BBS account that they can use to lobby for this?

... and Plogue say that MM must ask them to do it:

The ARIA VST3 needs to be updated for the multi channel features to work.

We cannot do this without MakeMusic requesting it.

Since Finale doesn't support VST3 that request seem unlikely

Finale on Mac doesn't use VST at all, yet there are ARIA Mac binaries for VST 2 and VST 3 plug-ins. And there's one the .aax plug-in used by ProTools.

Some people buy Garritan for use with other applications, and don't necessarily have Finale.

Yes, but, but my point is that it's unlikely for MM to make that request to Plogue