Way too cynical guys, it's much more nuanced than that.
Hospital administrators would be fine with animatronic rabbits staffing the ED if they provided reasonable d-to-d times and didn't cause core measure fallouts. But most hospitals are guided by an uneasy truce between what admin wants and what the high-volume proceduralists (surgery, interventional cards, etc) want. And if there's one thing high-volume proceduralists can't stand, it's slow turn-around times on their rooms. If there's two things they can't stand, it's the room thing and having to talk to midlevels calling from the ED. So I think that they'd be fine with midlevels from a monetary standpoint (especially if the APCs were hospital employees so they could directly pocket the savings), but I think they'd break out in a cold sweat thinking about their phone blowing up at 2am on a Saturday because Dr. Bypass got woken up by a midlevel.
Also, I'm not sure that there's any data that independent NPs get sued any more than MDs doing the same type of work. Part of that is going to be that their aren't many fields where case mixes are identical, part of that is going to be that being sued has only a tenuous relation to quality of care. I think there are EDs where staffing with a midlevel probably makes sense. I just got a flyer in the mail about EmCare trying to staff a low volume outpatient surgical hospital's ED offering 12-72h shifts. It's ridiculous to employee a BCEM to see 1-2 patients per day, but I could see it being a good fit for a CRNA since you're essentially looking for airway management and the ability to call the surgeon quickly.