Which is exactly what they were doing prior to Covid.
TPE began their recruitment process and was even looking at depot expansions, but then the global pandemic happened, passenger numbers dropped alongside the (then) planned timetable change for late 2021 which would have seen a TPE Liverpool to Nottingham replacing the EMR Liverpool to Norwich. (TPE even looked to eventually extend their Nottingham service to Leicester and this still remains on destination blind codes)
The DfT's stated position, at the time, was that the transfer would co-incide with an increase in local services in Lincolnshire though, which would balance out the loss of work at Nottingham. To some extent at least, that's now been catered for with an increase in establishment at a number of depots, so you'd be back to looking at potential redundancies, which is rather less than ideal.
May 2022 will be when decisions are made and nothing will change until then, and passengers (particularly in the west - including myself) will come to expect short formations and the current service unreliability that crewing a long distance service from only one end of the route will bring.
Short formations are a consequence of working an increasingly ancient fleet rather intensively, compounded by (maintenance) staffing issues, not an operator-specific issue. Newer trains should overcome that, regardless of the operator - and traction training the crews that already work the route would solve that much more quickly than recruiting and training new drivers and guards to cover the work at a different TOC.
Traincrew shortages are another thing altogether, of course, but it's a hopefully temporary shortage (of drivers in particular) that's the current problem, not the fact that it's resourced from one end. There is resilience, traincrew wise, in that drivers step back at Liverpool so there's always effectively a
useful spare there (it'd be ideal if guards did the same, but that's another story!) and the possibility of bouncing late-running trains straight back for a right-time start. Simplicity of diagramming has to be worth something too - they are (again, at least for drivers) all round trips from Nottingham, so you're unlikely to get traincrew out of position in a way that seriously hinders service recovery in the same way that you might if you have trains worked by a number of different depots and with relief en-route.