I don't think the business case is clear already, as we do not know the applicable regulations that ICAO and EASA will issue in terms of certification/operations/flight time limitations...
Let us have an example:
You can have singe pilot cruise ops (EMCO) certified by proving, among a load of other things, that the probability of an emergency descent multiplied by the probability of an auto emer des sytem failure stays below a certain safety threshold. What if one pack or one bleed is MEL? the probability of an emergency descent goes through the roof, as you have no redundancy anymore (been there...) .Still under that treshold? If not, no extended minimal crew operation today. Crew is augmented, or flight cancelled if no standby crew. And what if the failure happens in flight? Of course, you expect the second pilot to come back from the bunk. But then, what is the maximum flight duty period? The FDP originally planned with EMCO, or basic max FDP? Depending on the regulation, you may end up diverting for some very minor failures.
They can do it, ok. But will that be really profitable in the long run? Not sure. Time will tell...