The flying was transferred from a 737 to a 717 due to cost savings. Is the updated thrust required to do the job properly part of the new cost and how much cheaper is it really?
You assume it is about cost. It is about fulfilling the QF master plan, of breaking up mainline and replacing it with subcontractors.
Unfortunately at the rate they are going they could end up sinking the whole thing. Whether that is part of the plan or not is yet to be seen.