I think you should try out the technique and decide if it really produces better quality slo-mo before you worry about whether it is scriptable.

I watched the tutorial, was skeptical, and so I tried it out.

In no way does it force Vegas to do anything remotely similar to what Twixtor, Motionperfect, or other motion estimation-based slo-mo tools do. All Vegas does for slow mo is to, in essence, create additional new frames by crossfading adjacent frames. This provides very smooth, but also very soft, slow motion. The good news is that you never get any surprises, but the bad news is that the slow motion is fuzzy.

By contrast, motion estimation software looks at every small group of pixels, determines where they are going, and synthesizes all the intermediate frames. If it makes the correct choices, the new intermediate frames are sharp and clear and gorgeous. If it makes the wrong choices, you end up with strange, warped frames. Like the little girl in the old poem, when it is good, it is very, very good, but when it is bad, it is horrid.

The VASST technique shown in the YouTube video merely adds some additional in-between frames, and therefore really doesn't fundamentally change anything. In my brief tests, it actually seems to add more ghosting. This would tend to make the video look even smoother, but would also make it look even softer. My test confirmed this to be the case.

Try it out and see if you like the results, but my guess is that for most slo-mo work this would actually make the result look worse.

I'd be interested to hear other people's experience.

FWIW, I posted on my YouTube page, a long time ago, this example showing the difference between the various ways of doing slo-mo in Vegas, compared with doing the same thing using MVTools (a geeky, but free motion estimator that can be used for many interesting things, including slow motion):

http://www.youtube.com/user/johnmeyer77#p/u/25/UEfpP1zZKVs