I think you're grossly overestimating the fallout from this. I am the aforementioned business customer. Literally the only way you'd ever hit the dollar amounts they're looking for is flying multiple times across the Atlantic paying full fare business class - which I don't do. But I do fly multiple times a month across the continental US. Previously I would book Delta regardless of price for both business and personal travel due to status. They've made it basically unobtainable unless you're paying full fare first class on every flight AND booking your cars and hotel through them.
Going forward I'll just book the cheapest flight available and drop their card. They will be losing at minimum 10s of thousands a year in profit from my travel and card spend alone.