While a possibility, and has already been done in various guises, the drawback for commuting (for me) would be being too wide the filter past all the static cars stuck in thier traffic jam.
The main things that influence any variances in my journey time are my general wellbeing or the wind. Other traffic levels are not really a significant factor. If I had a wider HPV this would no longer be the case. Not only would I be held up in places, but I would imagine that there would also be places that I would be a major irritation for other road users who would be stuck behind me.
Thank you for a useful post.