I don't have any problem with encouraging convention delegates to stay at hotels who have accepted a rebate deal as long as disclosure is made and dealings are honest. It's normal for business conventions I attend and even things like class reunions, to book 200 rooms in a hotel and receive 10 free rooms and a meeting room and maybe one catered coffee and snacks lunch for meetings.
I'd have a problem with lack of disclosure and I'd have a problem with being "required" to stay at designated hotels. The Society could just say they get rebates and free rooms for Governing Body members and Bethel traveling staff to the listed Hotels. Me thinks the Society vastly underestimates the willingness to cooperate and they underestimate the generosity of the Witness people.
The Witness people aren't resisting the arrangements, they're resisting the spirit of the way the directions are given and they're resisting the appearance of being manipulated. Just be open and honest with them and I'd bet the people will willingly comply to a level not achievable by order directives and manipulations.