I remember we played a few matches with Martial and Rashford as two wide forwards(hug the line, provide width) and Mata as false-9. And it worked quite work(though Mata is not fast enough).
Maybe we could try again with Bruno/VDB as the false-9. With Martial and Rashford hugging the line, it would mitigate the problem of a diamond being too narrow.
In this case, we would have 3 options(Martial, Rashford, Greenwood) for the front 2 positions, and 2 options(Bruno, VDB) for the false-9, even if we failed to sign Sancho or anyone this summer.