Hi Geoff,
I think you make a good point, but it is also a very specific problem. It can be solved with look ahead buffering and extra computation within the VST. Adding extra tasks such as that will impact the ability to have lots and lots of VSTs implemented in a project at any given sample buffer timing. If that sort of feature is very important to you then I would use that capability as a defining point for choosing which VSTs are acceptable and of high enough quality for your use. I think that if I knew a particular effect was good, or not so good at it, that the info would effect my personal ideas regarding its value. I haven't thought much about it in the past, but if the info was more readily available I think I would.
It's my impression that free play musicians rarely ask me about tempo sync effects but they often wonder why I have switched the timeline to "time", abandoned using a M:B;T timeline, and adopted the use of markers to define the song form.
Getting a M:B:T timeline to match a live performance was one of the first expectations I had for "DAW" that seemed to be rewarded with frustration and disappointment.
As Jim mentioned, Cubase seems to have some really good timeline features, and if I could take the stress of learning yet another DAW I would have purchased a license in the past few years just for those features.