Great points. Allow me to make some observations.
I believe that the door to door ministry is not the way to make the most converts, but it is the easiest way to control the 2 variables that the GB can least control, who preaches, and who accepts.
Imagine if blogs were allowed. Then the message is out of the control of the GB. If it were on TV, then it actually exposes the JW dogma to too many people. When "new/social" media came out, the GB was wisely slow for their own interests in adopting it, because it would change the flow of information from a trickle to a fire hose level.
Terry, one thing your essay here brings to mind as you have alluded to, is that JW's cannot grow as fast as they did before 1975. It is almost impossible to replicate those circumstances. In fact, I would suggest that the information age has made it imperative for the surivival of JW's to slow down information as opposed to getting your dogma out more quicly. (which of course, flies in the face of the "urgency" of the JW message)
Clearly, the door to door method is the easiest way to continue to allow JW's to select those that show interest and to make sure that they are properly indoctrinated first. Screened as it were.
If someone responded to a TV show and went to a KH based on the typical initial message of JW's (i.e. Hey, how does paradise sound to you?) and then spent time and found out that no such paradise exists, then more people at the same time would point the same finger at the same problems of JW's.
But if one lonely soul thinks it sounds good, agrees to a study, an in a month, comes to the correct conclusion that JW's are kooks, then they simply stop going. No one else to complain to, after all, you let them in your own home, and stopped them from coming after a while.
It is all damage control.
I don't think that as it is now was part of the plan, it has clearly evolved in this. But the GB since Knorr and esp since 1975 have been slooooooow to adopt anything that would in real terms, speed up the preaching work.
If speeding up the preaching work = losing control of the work, then the GB will obviously want no part of it.