How do we salvage something from this disaster?
Dig the tunnels to Euston.
Select whichever design of Euston allows for 16tph (eventually) - and just build in the cheapest way possible. In stages if necessary. Don't involve private developer capital - the value they will extract comes from the taxpayer.
Build the cheaper version of the Handsacre spur, onto the WCML slows
Extend platforms to 400m at Crewe, Preston, Warrington BQ, Carlisle
Build 2a to Hixon, with a chord towards Stoke
Build a chord to connect Delta Junction to the Birmingham-Derby line
Then safeguard the rest of the HS2 route - all the way to Manchester, Leeds, Wigan. Spend money on buying the properties, but then rent or lease them back out on fixed term leases, which all terminate in, say, 2040 (west) or 2045 (east) when the next phase of construction can start.
In the meantime, stop wasting money on marginal upgrades to the rest of the network which will become redundant when HS2 is completed.