It's a good question and I am thinking about it. I'm not sure there is a way to measure it. Sometimes only a disaster is apparent.
Airlines have to guess whether RR redemptions displace or substitute for cash ticket sales. There is no good way to know, except if cash sales drop precipitously.
We might be limited to running a member opinion survey after the test.
So, if it isn't a disaster, it sounds like you at least will declare it a success, and even with about 50% of the people not wanting it, will proceed?
What good is the member opinion survey if the results are split the same, or if people don't participate in that?
I really think this is a solution in search of a problem.