I'm sure improvements can be made to platform lengths, signals, timetables and infrastructure to avoid building a new line into Euston .
What though?
Anti-HS2 people are quick to suggest that we could just spend that money on upgrading the existing network, which sounds a nice argument, but what realistic/ affordable/ simple changes could you make on the WCML?
There's nine "fast" services an hour already (3x Birmingham, 3x Manchester, one to Glasgow, one to Liverpool, one to Chester/ Holyhead)...
...there's peak extras for Liverpool too.
The majority of 390s are eleven coaches, so I don't think the infrastructure could take much more (bear in mind that the cab vehicles are over twenty five metres long, the intermediate vehicles around twenty four metres long).
You could get some more capacity by expanding the remaining ones to eleven coaches, but that limits where they can run (e.g. platforms at Lime Street).
Replace Voyagers with something longer? Fair enough, though that doesn't make much difference to the main markets (Birmingham and Manchester to London). You then create the problem that there's no bi-mode train capable of tilting (to reach over 110mph on the WCML) - or do you abandon through services to Holyhead etc?
LM are running twelve coach services out of Euston, so not much more scope to increase those.
Norton Bridge will make some improvements, but too often with these kind of schemes you just find yourself running into the next bottleneck up the line.
You could try remodelling places like Crewe (to allow more services to run by grade separating), but that's going to cost silly money and mean the current route is disrupted for a long time.
Longer platforms will generally mean fouling junctions - of major disruption if you try to do this at the "buffer end" of termini.
We've four tracked routes already, and any further loops are going to potentially mean demolishing the various houses/ businesses that back onto the WCML.
Erm... 3+2 seating on Pendolinos? A handful of seats by removing a couple of toilets? I jest, but I really don't know what the alternatives are.
Stand at somewhere like Milton Keynes for half an hour, watch all the 200m+ trains try to cope with 2016 capacity - imagine how much more capacity you'll need for the 2030s if population/ travel continue to increase.
We've done all of the "easy" stuff - we are struggling to meet current demand - there is no magic bullet. I get that some people don't want HS2, I get that it's not going to benefit everywhere, maybe I'd do things slightly differently if I were in charge, but I can't see a realistic better option.
If you are more of an expert than the professionals then I'd be interested in hearing your ideas though.