Personally, I believe they should be reconfigured into a handful of 400m sets and a fleet of ~275m sets.
However, the powers that be are opposed to such moves because it appears they still hope to ressurrect the programme.
As a result it appears likely that we will be stuck with a woefully inappropriate rolling stock fleet for the next 30 years.
I am inclined to agree with this. Though I'd look at what work would be necessary to use 300m single sets particularly on Manchester services, which would if feasible provide a very significant capacity increase on now.
Alternatively work could be done to give a limited set of stations (e.g. Crewe and Manchester Piccadilly*) 400m platforms to allow for a timetable based on splitting and joining. Maybe this would be better. You could do things like run Euston-Crewe 400m non stop then split with one calling at Preston, Carlisle, Motherwell and Glasgow and the other half Warrington, Wigan, Preston, Lancaster, Oxenholme, Penrith and Carlisle (maybe also onto Haymarket and Edinburgh to add capacity that way). Or if pathing is easier include the Liverpools.
It might be that these platforms are cheaper than reconfiguring the unit order and depot.
There are also other places 200m units might be handy, e.g. Manchester-Birmingham and Manchester-Scotland (the latter is rapidly outgrowing 5-car sets, with fake-"sold out" coming up far more often on these than Avanti services). Or TPE post wires?
* In that case it would mean 400m x 3 per hour - there is room on the car park for two 400m platforms. ASDO could be used at other stations, though it could require some points to be moved.