Want to add more pressure?
perform the bookstudy in 30 minutes.
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two 5 minutes (one by a brother and one sisters) (assigned by the elder to members of the bookstudy group) - no signup for this assignment required, it's not officially the school but a preparation to join the school or better your speaking habits in a smaller more intiimate group.
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a 5-10 minutes bible reading (by a brother, of course!)
The talks could be assigned by the BSO and his assistant. The added pressure of having a part may force certain ones to show up when they otherwise would not. It could also be sold as a means to prepare certain ones who are nervous about giving talks at the KH to do so and to prepare everyone for more informal witnessing.
PLUS, since we're so close to the end the WTS would easily see the rumor spread that this change was due to the persecution that they see 'right around the corner.'
Just my opinion.