I can think of a way they could turn this around to their advantage.
The fact is that door to door preaching was never very effective anyway. Many converts have tended to come into the religion through extended family, friends, schoolmates, coworkers, and neighbours, rather than door to door work. This is true not only of JWs but for many conversionist religious groups. Informal networks have always produced more converts than formal preaching.
So Watchtower could lay a heavy stress on JWs trying to convert family, friends and acquaintances. They could say the new emphasis has been forced by Caesar’s law and they are obediently changing their method but not decreasing their zeal! They could emphasise inviting people to the meetings to see what it is like for themselves. Don’t just invite people but offer to pick them up and physically bring them along.
If this was part of a deliberate strategy then they could also consider improving the quality and enjoyability of their meetings, especially on the bring a friend day. Maybe even designate the first Sunday of the month “bring a friend” day. Include a practical talk on an interesting topic, allow discussion, and offer food after the meeting.
What door to door ministry remains could have a heavy focus on inviting people to the meetings on the first call, making definite plans, and again offering to pick them up and bring them to the KH.
Of course JWs face the problem that they are not supposed to keep close friendships outside the religion, but it’s a fine line that I am sure Watchtower could navigate to their advantage, if they wished.
This suggestion might not produce the heady growth they once enjoyed, such as the early 70s. It is likely nothing could produce such growth again, because society has changed. But this approach might just about ensure rising numbers rather than decline, if implemented effectively.