But surely 3x5 coach trains is better than 1x7 and 2x4 overall?
Oh ok, so as a solution to overcrowding on one of the constantly busiest routes in the UK, when additional carriages come available for it, were just not going to use all of them? Makes sense.
Same as above
So we want extra trains, so that we can put a load of carriages unnecessarily into store because we want these "ideal" 7 coach voyagers?
Firstly I am not saying that we should have them, rather what might happen beyond the next few years to try and give XC a better length of train as short trains appear to be the problem that they are suffering from.
It does very much depend on what the future policy is. For instance once MML, ICWC and XC stops needing the class 22x's in quite such large numbers then there come the problem of what to do with them. As there are only so many IC routes where they are of use it may well be that putting some of the end coaches in store so that other sets can be longer is the best future for them.
For instance if the ICWC franchise gets rid of all their voyagers then that is 20 sets of 5 coach trains which is a lot of trains to find a new route to cover when many of the existing IC routes are becoming electrified or at least mostly electrified so any extra services run on those routes are likely to be short lived. As such it may be that it is better for these trains to be 12 sets of 7 coach trains, 10 sets of 8 coach trains or ever 7 sets of 10 coach trains (plus 2x4 coach trains) or any other possible combination to improve capacity on key routes rather than run more and more doubled up serviced.