Since FC upgrades are now effectively impossible due to WFBC monetization strategy, the obvious next step is applying this model to Comfort or Premium Select cabins.

I stopped expecting any kind of upgrade from Main years ago as I flip-flopped between GM and FO flying mainly domestic U.S. in Main/"Economy Discomfort", although they happened a fair amount of the time. As others mention upstream, it will be effective at getting kettles or infrequent flyers to spend more for what they think is a premium product, thus taking away more free upgrade inventory. Even if that product is an effectively marginal few inches more legroom while sharing armrests, and a bag of 0.5oz of premium kettle chips (no pun) instead of a Biscoff.

Whenever I do need Comfort or PS, it's on long-haul international usually paid for with cash money or sometimes miles, and in seats I select - away from toilets.