What would be the impact of replacing the engines on the 737 MAX, not just reworking MCAS?
Possible? Yes.  Economically feasible, not even close.  To re-engine the plane, you would basically have to re-do a large amount of the FAR 25 certification.  Right now, Boeing has to re-do one thing, and it will take a few months.  To re-engine the plane would take several years at the least.  However much money it is losing right now, it is a drop in the bucket compared to the cost of what you propose.