I was reading another article that said they'd considered that and shitcanned the idea.
Ah,
here it is. FTA: "First, it wants new — not refurbished — systems and intends to
maintain an eight-engine configuration on each B-52, knocking out competitors who have floated a four-engine solution.
The engines must be able to be integrated without having to significantly rework the B-52’s wings, although the service expects some design changes to structures such as struts and nacelles may be necessary. "