I think it could be a cool feature with some sort of combined instruments. Basically it would work just like two instruments playing the same notes on the same channel, except one wouldn't have to go thru the hassle of duplicating channels. What's the point in that, I hear you say?
Well, for one it would be an easy way to make new inspiring sounds. Another possible benefit for the future would be the ability to better handle multisampled instruments with layered sounds, such as some soundfonts. Any effect commands would be applied to all instruments included in the combined superinstrument.
Perhaps not the best explanation, but if you have any questions regarding this please don't hesitate to ask as I think this could be a really useful feature.
Sorry for bumping, but does the overwhelmingly underwhelming response mean that this fantabulous idea needs time to sink in or that it just sucks?
let's put it like this: it's currently impossible.