The 170s will be improved with the extension of some to three coaches after EMR take on the various 170/171s, and I think that's enough of a solution for now.
Not sure may long-suffering passengers on the Birmingham-Cardiff route in particular would agree with that.
It may improve conditions on the services currently diagrammed for two-car 170s that can go up to three-cars but much of the time all that will means is that passengers will have a better chance of getting a seat.
It will not do a thing to address the fundamental need to provide something for that route with rather more than 180 seats per train - and a four car 22x is not that something.