I think there's at least a not-entirely-irrational "So, did they miss anything else?" fear here. I'd be inclined to recommend some mix of switching to (similarly-sized) 757s where possible and moving any shorter-term 737 MAX orders down to "standard" 737 planes.

This isn't a full-blown cancellation, but I think a demand of "You will go back, review everything, and assure us that there's not another disaster lurking in the wings and we'll go from there" isn't unreasonable, even if it fouls up fleet replacement timetables. However, something else coming along and grounding the plane again in a year or two (even if it is a preemptive catch)? That's gonna be a problem for everyone.

Edit: Also, I don't think Boeing will have much (if any) luck penalizing anyone who dumps a MAX order because of this, given the obvious mess they made of the process. If anything, they're probably "on the hook" for damages from folks who already have aircraft in hand who just saw big chunks of their fleet grounded.