I think the size and existing supply chain and infrastructure would be big plusses for a reengined 767.
The 767-400ER and recent KC46 invested a lot in updates on the 767 cockpit and legacy systems.
Empty weight of a reengined would be 30t lower than the 787 and A330s, and its fuel consumption 15-20% lower then RR, PW , GE powered 767-300ER.
Still way more capable than a A321 XLR. GE, US DoD, United, FEDEX, UPS would certainly support the business case.
