Looking through the thread, there doesn't seem to be an issue from a passenger perspective with the current services in terms of timetabling. The current half hourly services on the core network is good.
However, I'm not writing from an enthusiasts point of view - just someone who is interested in why my regular travel is in the state it is in, so pardon me if I make a few naive errors.
The procurement of the Voyagers obviously suffered from the short-sighted small time attitude that seems to be inherent on the British railways. Whoever thought that 4 car trains, effectively 3 when you discount first class, would be sufficient capacity for reasonably fast trains linking all of the UK's major cities other than London is stupid.
It is the same with the WCML and HS2. If Birmingham was connected to the 'WCML proper' on 4 tracks, and there was the standardised 4 tracks that we now have in the Trent Valley throughout the WCML and ECML then there'd be less of a need for HS2. If the DfT, government, Railtrack or whoever weren't so incompetent and they actually managed to deliver the 140mph running, then we wouldn't need it at all. Currently, the fastest New Street to Euston train is 1 hour 12 minutes. Obviously this is slowed down by the slow running to Rugby. If there were 4 lines out of New Street and 140 mph running, it could probably get down to a 1 hour service - therefore the 15 minute saving by building HS2 wouldn't be worth it. If in the 60s when they redeveloped New Street, they had done it properly then we wouldn't be strangled with the infrastructure problems we have today. 2 lines in and 2 lines out to the biggest station in the 2nd city - joke!
And the lack of vision and foresight from the 60s and previously still continues today. The highly insufficient Voyagers, the 3 car 185s. Surely they could've learnt from the Voyager capacity errors. But no, absolutley no provision for growth or even sufficient capacity in the present.
As has been stated previously in the thread, we need those extra carriages on the Voyagers as a minimum. How about standardising the fleet of the different routes and TOCs as well. Cascade all of Virgin's 221s to CrossCountry so after 'extra carriaging' there'd be a mixture of 5 and 6 car voyagers across the network.
Replace the VT Voyagers with Pendolinos and a few more locomotives if required for haulage on the North Wales/Chester lines.
Move the HSTs to provide extra capacity with current HST fleets. Then the DfT and TOCs need to collaborate and source an adequate replacement for the HSTs.
Meanwhile we have the refurbishment and addition of carriages to the Voyagers and maybe the Derby Bombardier plant will stay open. There'd be ample capacity for doubling and they wouldn't be too long for the shorter platforms.
I don't find the Voyagers too bad. Yes, they smell at times, they do rattle, are noisy and they are in need of a refurb. BUT, I'd much rather do a Manchester-Birmingham run on them, then say a Manchester-Blackburn run on a 150, Pacer or other inadequate 1980s excuse of a train.
Surely, the toilet issue can be rectified or at least mitigate the smell. The layout isn't too bad. The window issue can be lived with - pretty similar issue on the Pendos as well. Replace the seats. The Virgin offering isn't too bad. Re-do the air-con so there's a consistent temperature, not either freezing throughout the carriage and then red hot under the vent in the ceiling next to the vestibule doors and sort out the luggage facilities. How about gutting the old shop/luggage compartment, removing the ducting/ventilation and putting in extra seats and put extra luggage racks throughout the train.
Lastly, replace the audio system and visual displays to a combo of the Pendo system and the London Midland 350 set-up.