Knowing First groups love of packing drivers diagrams as much as they can, I'd say once crewe comes on stream, Liverpool drivers may end up doing 2 or 3 trips per day to crewe with a crewe or london man doing the crewe to london section of a liverpool to euston run.
Apparently this is more productive, however I'd argue it would be counter productive. I hope attitudes within First change in time that it isnt what happens on avanti as it is slowly happening on GWR
TPE and SWR have a lot of traincrew relieving en route. It may be slightly more efficient on paper, however it falls on its face when there is service disruption!