One thing with volume fade-ins you could do is put 0F first and then after a gap put a sustain envelope of the appropriate volume, and repeat. So that it maybe goes:
That's just a guesstimate but that kind of technique might be good.
I've done this a few times (actually, I did just this last night on something I was working on, heh) but it's pretty hard to nail exactly where to trigger the sustain, it takes a lot of experimenting to not get a noticable volume jump.. but it works well when you do hit upon it.