There is an older thread of mine in which I tried the stretch feature in VI Pro to alter the envelope of the progressive vibrato in a way that it would kick in earlier, at least I was trying. Can't remember the thread; but anyway it didn't work. :D
What I meant in my previous post: At first I really wished that the vibrato would kick in earlier, but actually I like it the way it is. You have to wait until it kicks in, this is true, but the louder you get with Velocity XF the more it kicks in earlier, isn't it? I don't know if this is only my imagination. If I really want molto vibrato, then I also play forte or fortissimo. Of course, you can't have this "espressivo pianissimo" as in Synchron Strings Pro.
I always associate molto vibrato with louder volumes, and I think this is the reason why the VI libraries sound very natural because of the "baked-in" vibrato: The louder you get, the more vibrato you have. I'm not a big fan of vibrato crossfades and this is one of the reasons why I don't like Synchron Strings (Pro). Would be nice to have a progressive vibrato, too.