So we basically have a stretched version of an existing type with larger diameter engines which needs software to correct handling issues. Sound familiar ?
Boeing can't afford another MAX debacle with a new type, a disaster with an aircraft of this size would be far worse. The FAA can't be seen to lack oversight a second time.
The entire project needs to be halted whilst Boeing and the FAA go through every step of the design and construction with a fine tooth comb and fix any deficiencies before it gets signed off. The cost of this would pale in comparison to a hull loss and the resulting consequences.