I wouldn't want to have to rendezvous at a time and place. That would kill this idea.

You'd also have to take into account people with small kids. I wouldn't use this if I had to stay in the convoy for the whole trip. I like to stop fairly frequently, otherwise the kids get bored, restless and upset.

I think it's likely only to work if you get on the motorway catch up to a convoy and then join it - Which I think is the way this works.