I'm going to add to all of the above that there's a way to sort-of "split the baby" - you could give the RDMs a cash value on tickets that pegs to the price for sale (say, £0.01/point for BA - treatment of taxes can go either way) but you give bonuses on the redeemable value if you have status or certain types of relationship with the program (e.g. 25%/50%/75%/100%). That means that your CC-only folks are likely to only be at the lower tiers while "actual" frequent flyers will inherently get better value out of the program. This also avoids the fail-states that I described above (offers that mismatch with consumer preferences).

I would also point out that the author completely ignores the business model of "Delta, a division of American Express" as a viable one. It's definitely easier in the US, but something like that is something to consider and it seems to be where things are going.