Amazing the # of times that letter refers to "personal choice" when the company wants to tell you what they are NOT going to pay for certain things overseas (...your housing, your car, your kids education, etc...)
But then is asking for NEW AUTHORITY to implement a non-voluntary inverse to a 90-day STV if they can't sell enough of their "enhanced LOA move packages" to fill the slots.
Keep SIBA...or offer the trips as part of the monthly bid pack.
If they go unfilled, then pay DRAFT --- that way it truly is "personal choice"!
It's still a "NO" --- get back to the table and negogiate.