Crosstudio - one thing you could try is setting up extra virtual mains. Then assign the things you want to group together to the same Main, and simply put an envelope on the Main (rather than, or in addition to, those on the individual tracks).
I do a lot of stuff with background vocals. So frequently I "solo" just the backgrounds, and then use envelopes on each track to get the volumes among the tracks to blend well. But when I un-solo them I sometimes find that they are too loud (or too soft) relative to the lead vocal. What to do - since I just spent all that precious time blending them. I don't want to change the balance between them, which I risk doing if I adjust the envelopes or the volume levels of the individual tracks.
In this case I assign the background vocals to their own, unique VM, and then I can either raise or lower the volume setting on the main itself, or if I just need to adjust certain sections, use an envelope on the VM. So the overall volume can be adjusted, without effecting the ratio among the tracks (essentially the same as grouping - but easier IMHO).
The fact that they are virtual mains, allows you to assign multiple VMains to the same physical outputs on your sound card (e.g., Delta 3/4). This way you won't run into problems when you mix down to wave (you do need to deselect "send each source to separate submix" though).