There are many many threads which have debunked any idea that 222s could be an appropriate fleet for that route. They are totally inappropriate for Nottingham to Liverpool, no matter what could be done with the 158s as a result. As their home at Derby becomes a Hitachi depot with the coming of the 810s, they are also without suitable servicing facilities on the EMR network.
You make a good point regarding the future servicing of 222's, but the other two main debunks are themselves open to debunking.
222's indeed are restricted to 70mph over the Hope Valley and unable to utilise the SP speed differentials. However, many of those differentials are just paper excercises and not attainable by a 158. The much greater acceleration of the 222 means they can match 158 timings, as has been demonstrated when utilised on Aintree race days.
The other issue is seating. A lot is made of the fact that a 5 car 222 has less seats than a pair of 158s. When the 158s were refurbished though, it was done on flawed data on passenger numbers, and it was decided that if the absolute maximum number of seats was crammed in a 2 car 158, it would be sufficient. It was soon found out that seating was still insufficient and so the service was increased to 4 cars, all with seats crammed in at the expense of space for luggage, which ended up dumped in aisles, vestibules, and on surplus seats. I'm sure a 5 car 222 would strike a healthy balance between seat availability, and luggage room. I haven't signed Liverpool for nearly three years now so that may or may not still be the case.
I do accept that a 222 has an insane appetite for fuel when compared to a 158. I think it's an exaggeration to say they are wholly inappropriate though.