Folding ROSCOs ( including procurement ), crew & staff into NR & letting NR train crew so they could work regionally instead of just a TOC's services might be a start. DFT already decides the service & effectively the money, so what's left is branding & bookkeeping & at that point it hardly matters if you brand every individual service or large areas, from an operational point of view. And, well, there's some wiggle room for private management & even stock hire there.
A better question might be "should the DFT take a step back from operating the railways", then you might have to decide about a structure resembling the old sectors. Are we talking branding or complete management?