The problem is that airlines often like to enhance away the most popular selections and then say "based on customer feedback". (because often popular = used a lot = expensive to provide)

Any half-decent data analyst can already see from their internal data which benefits members are actually using. They can probably even infer that members who ONLY travel TK using upgrade vouchers are only travelling TK WHEN they can use the upgrade vouchers. (to choose one example that I fear will be enhanced away)